:root {
  /* Academic Color System - Modern Institution Palette */
  
  /* Pure Foundation Colors */
  --color-white: rgba(255, 255, 255, 1);
  --color-black: rgba(0, 0, 0, 1);
  
  /* Slate Scale - Primary Grays for Academic Hierarchy */
  --color-slate-50: rgba(248, 250, 252, 1);   /* Softest background */
  --color-slate-100: rgba(241, 245, 249, 1);  /* Card backgrounds */
  --color-slate-200: rgba(226, 232, 240, 1);  /* Borders */
  --color-slate-300: rgba(203, 213, 225, 1);  /* Subtle borders */
  --color-slate-400: rgba(148, 163, 184, 1);  /* Disabled text */
  --color-slate-500: rgba(100, 116, 139, 1);  /* Secondary text */
  --color-slate-600: rgba(71, 85, 105, 1);   /* Body text */
  --color-slate-700: rgba(51, 65, 85, 1);    /* Emphasis text */
  --color-slate-800: rgba(30, 41, 59, 1);    /* Headings */
  --color-slate-900: rgba(15, 23, 42, 1);    /* Primary text */
  
  /* Academic Blue - Authority and Trust */
  --color-blue-50: rgba(239, 246, 255, 1);
  --color-blue-100: rgba(219, 234, 254, 1);
  --color-blue-500: rgba(59, 130, 246, 1);   /* Primary interactive */
  --color-blue-600: rgba(37, 99, 235, 1);    /* Primary hover */
  --color-blue-700: rgba(29, 78, 216, 1);    /* Primary active */
  
  /* Semantic Reds for Errors */
  --color-red-50: rgba(254, 242, 242, 1);
  --color-red-500: rgba(239, 68, 68, 1);
  --color-red-600: rgba(220, 38, 38, 1);
  
  /* Success Green */
  --color-green-50: rgba(240, 253, 244, 1);
  --color-green-500: rgba(34, 197, 94, 1);
  --color-green-600: rgba(22, 163, 74, 1);
  
  /* Warning Amber */
  --color-amber-50: rgba(255, 251, 235, 1);
  --color-amber-500: rgba(245, 158, 11, 1);
  --color-amber-600: rgba(217, 119, 6, 1);
  
  /* RGB versions for opacity control */
  --color-slate-900-rgb: 15, 23, 42;
  --color-slate-800-rgb: 30, 41, 59;
  --color-slate-700-rgb: 51, 65, 85;
  --color-slate-600-rgb: 71, 85, 105;
  --color-slate-500-rgb: 100, 116, 139;
  --color-blue-500-rgb: 59, 130, 246;
  --color-blue-600-rgb: 37, 99, 235;
  
  /* Semantic Color System - Academic Professional */
  --color-background: var(--color-white);              /* Pure white for maximum clarity */
  --color-surface: var(--color-slate-50);              /* Card backgrounds */
  --color-surface-elevated: var(--color-white);        /* Modal/dropdown backgrounds */
  
  /* Text Hierarchy - Enhanced Contrast for Readability */
  --color-text-primary: var(--color-slate-900);        /* Titles, important content - WCAG AAA */
  --color-text-secondary: var(--color-slate-700);      /* Body text, descriptions - Enhanced contrast */
  --color-text-tertiary: var(--color-slate-600);       /* Meta info, captions - Still readable */
  --color-text-disabled: var(--color-slate-400);       /* Disabled states */
  
  /* Interactive Elements */
  --color-primary: var(--color-blue-500);              /* Links, primary buttons */
  --color-primary-hover: var(--color-blue-600);        /* Hover states */
  --color-primary-active: var(--color-blue-700);       /* Active/pressed states */
  
  /* Borders and Dividers - Enhanced Visibility */
  --color-border-subtle: var(--color-slate-200);       /* Soft separators */
  --color-border-default: var(--color-slate-300);      /* Standard borders - More visible */
  --color-border-emphasis: var(--color-slate-500);     /* Strong borders - High contrast */
  
  /* Status Colors */
  --color-error: var(--color-red-500);
  --color-error-bg: var(--color-red-50);
  --color-success: var(--color-green-500);
  --color-success-bg: var(--color-green-50);
  --color-warning: var(--color-amber-500);
  --color-warning-bg: var(--color-amber-50);
  --color-info: var(--color-blue-500);
  --color-info-bg: var(--color-blue-50);
  
  /* Focus and Selection */
  --color-focus-ring: rgba(var(--color-blue-500-rgb), 0.5);
  --color-selection: rgba(var(--color-blue-500-rgb), 0.1);
  
  /* Typography Scale */
  --font-family-base: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, 
                      "Helvetica Neue", Arial, sans-serif;
  --font-family-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, 
                      Monaco, Consolas, monospace;
  --font-size-xs: 11px;
  --font-size-sm: 12px;
  --font-size-base: 14px;
  --font-size-md: 14px;
  --font-size-lg: 16px;
  --font-size-xl: 18px;
  --font-size-2xl: 20px;
  --font-size-3xl: 24px;
  --font-size-4xl: 30px;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 550;
  --font-weight-bold: 600;
  --line-height-tight: 1.2;
  --line-height-normal: 1.5;
  --letter-spacing-tight: -0.01em;

  /* Spacing */
  --space-0: 0;
  --space-1: 1px;
  --space-2: 2px;
  --space-4: 4px;
  --space-6: 6px;
  --space-8: 8px;
  --space-10: 10px;
  --space-12: 12px;
  --space-16: 16px;
  --space-20: 20px;
  --space-24: 24px;
  --space-32: 32px;

  /* Border Radius */
  --radius-sm: 6px;
  --radius-base: 8px;
  --radius-md: 10px;
  --radius-lg: 12px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.02);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04), 0 1px 2px rgba(0, 0, 0, 0.02);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.04),
    0 2px 4px -1px rgba(0, 0, 0, 0.02);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.04),
    0 4px 6px -2px rgba(0, 0, 0, 0.02);
  --shadow-inset-sm: inset 0 1px 0 rgba(255, 255, 255, 0.15),
    inset 0 -1px 0 rgba(0, 0, 0, 0.03);

  /* Animation */
  --duration-fast: 150ms;
  --duration-normal: 250ms;
  --ease-standard: cubic-bezier(0.16, 1, 0.3, 1);

  /* Layout */
  --container-sm: 640px;
  --container-md: 768px;
  --container-lg: 1024px;
  --container-xl: 1280px;
}

/* Dark mode colors */
@media (prefers-color-scheme: dark) {
  :root {
    /* RGB versions for opacity control (Dark Mode) */
    --color-gray-400-rgb: 119, 124, 124;
    --color-teal-300-rgb: 50, 184, 198;
    --color-gray-300-rgb: 167, 169, 169;
    --color-gray-200-rgb: 245, 245, 245;

    /* Background color tokens (Dark Mode) */
    --color-bg-1: rgba(29, 78, 216, 0.15); /* Dark blue */
    --color-bg-2: rgba(180, 83, 9, 0.15); /* Dark yellow */
    --color-bg-3: rgba(21, 128, 61, 0.15); /* Dark green */
    --color-bg-4: rgba(185, 28, 28, 0.15); /* Dark red */
    --color-bg-5: rgba(107, 33, 168, 0.15); /* Dark purple */
    --color-bg-6: rgba(194, 65, 12, 0.15); /* Dark orange */
    --color-bg-7: rgba(190, 24, 93, 0.15); /* Dark pink */
    --color-bg-8: rgba(8, 145, 178, 0.15); /* Dark cyan */
    
    /* Semantic Color Tokens (Dark Mode) */
    --color-background: var(--color-charcoal-700);
    --color-surface: var(--color-charcoal-800);
    --color-text: var(--color-gray-200);
    --color-text-secondary: rgba(var(--color-gray-300-rgb), 0.7);
    --color-primary: var(--color-teal-300);
    --color-primary-hover: var(--color-teal-400);
    --color-primary-active: var(--color-teal-800);
    --color-secondary: rgba(var(--color-gray-400-rgb), 0.15);
    --color-secondary-hover: rgba(var(--color-gray-400-rgb), 0.25);
    --color-secondary-active: rgba(var(--color-gray-400-rgb), 0.3);
    --color-border: rgba(var(--color-gray-400-rgb), 0.3);
    --color-error: var(--color-red-400);
    --color-success: var(--color-teal-300);
    --color-warning: var(--color-orange-400);
    --color-info: var(--color-gray-300);
    --color-focus-ring: rgba(var(--color-teal-300-rgb), 0.4);
    --color-btn-primary-text: var(--color-slate-900);
    --color-card-border: rgba(var(--color-gray-400-rgb), 0.2);
    --color-card-border-inner: rgba(var(--color-gray-400-rgb), 0.15);
    --shadow-inset-sm: inset 0 1px 0 rgba(255, 255, 255, 0.1),
      inset 0 -1px 0 rgba(0, 0, 0, 0.15);
    --button-border-secondary: rgba(var(--color-gray-400-rgb), 0.2);
    --color-border-secondary: rgba(var(--color-gray-400-rgb), 0.2);
    --color-select-caret: rgba(var(--color-gray-200-rgb), 0.8);

    /* Common style patterns - updated for dark mode */
    --focus-ring: 0 0 0 3px var(--color-focus-ring);
    --focus-outline: 2px solid var(--color-primary);
    --status-bg-opacity: 0.15;
    --status-border-opacity: 0.25;
    --select-caret-light: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23134252' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    --select-caret-dark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23f5f5f5' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");

    /* RGB versions for dark mode */
    --color-success-rgb: var(--color-teal-300-rgb);
    --color-error-rgb: var(--color-red-400-rgb);
    --color-warning-rgb: var(--color-orange-400-rgb);
    --color-info-rgb: var(--color-gray-300-rgb);
  }
}

/* Data attribute for manual theme switching */
[data-color-scheme="dark"] {
  /* RGB versions for opacity control (dark mode) */
  --color-gray-400-rgb: 119, 124, 124;
  --color-teal-300-rgb: 50, 184, 198;
  --color-gray-300-rgb: 167, 169, 169;
  --color-gray-200-rgb: 245, 245, 245;

  /* Colorful background palette - Dark Mode */
  --color-bg-1: rgba(29, 78, 216, 0.15); /* Dark blue */
  --color-bg-2: rgba(180, 83, 9, 0.15); /* Dark yellow */
  --color-bg-3: rgba(21, 128, 61, 0.15); /* Dark green */
  --color-bg-4: rgba(185, 28, 28, 0.15); /* Dark red */
  --color-bg-5: rgba(107, 33, 168, 0.15); /* Dark purple */
  --color-bg-6: rgba(194, 65, 12, 0.15); /* Dark orange */
  --color-bg-7: rgba(190, 24, 93, 0.15); /* Dark pink */
  --color-bg-8: rgba(8, 145, 178, 0.15); /* Dark cyan */
  
  /* Semantic Color Tokens (Dark Mode) */
  --color-background: var(--color-charcoal-700);
  --color-surface: var(--color-charcoal-800);
  --color-text: var(--color-gray-200);
  --color-text-secondary: rgba(var(--color-gray-300-rgb), 0.7);
  --color-primary: var(--color-teal-300);
  --color-primary-hover: var(--color-teal-400);
  --color-primary-active: var(--color-teal-800);
  --color-secondary: rgba(var(--color-gray-400-rgb), 0.15);
  --color-secondary-hover: rgba(var(--color-gray-400-rgb), 0.25);
  --color-secondary-active: rgba(var(--color-gray-400-rgb), 0.3);
  --color-border: rgba(var(--color-gray-400-rgb), 0.3);
  --color-error: var(--color-red-400);
  --color-success: var(--color-teal-300);
  --color-warning: var(--color-orange-400);
  --color-info: var(--color-gray-300);
  --color-focus-ring: rgba(var(--color-teal-300-rgb), 0.4);
  --color-btn-primary-text: var(--color-slate-900);
  --color-card-border: rgba(var(--color-gray-400-rgb), 0.15);
  --color-card-border-inner: rgba(var(--color-gray-400-rgb), 0.15);
  --shadow-inset-sm: inset 0 1px 0 rgba(255, 255, 255, 0.1),
    inset 0 -1px 0 rgba(0, 0, 0, 0.15);
  --color-border-secondary: rgba(var(--color-gray-400-rgb), 0.2);
  --color-select-caret: rgba(var(--color-gray-200-rgb), 0.8);

  /* Common style patterns - updated for dark mode */
  --focus-ring: 0 0 0 3px var(--color-focus-ring);
  --focus-outline: 2px solid var(--color-primary);
  --status-bg-opacity: 0.15;
  --status-border-opacity: 0.25;
  --select-caret-light: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23134252' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
  --select-caret-dark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23f5f5f5' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");

  /* RGB versions for dark mode */
  --color-success-rgb: var(--color-teal-300-rgb);
  --color-error-rgb: var(--color-red-400-rgb);
  --color-warning-rgb: var(--color-orange-400-rgb);
  --color-info-rgb: var(--color-gray-300-rgb);
}

[data-color-scheme="light"] {
  /* RGB versions for opacity control (light mode) */
  --color-brown-600-rgb: 94, 82, 64;
  --color-teal-500-rgb: 33, 128, 141;
  --color-slate-900-rgb: 19, 52, 59;
  
  /* Semantic Color Tokens (Light Mode) - Updated to Academic */
  --color-background: var(--color-white);
  --color-surface: var(--color-slate-50);
  --color-text: var(--color-text-primary);
  --color-text-secondary: var(--color-text-secondary);
  --color-primary: var(--color-blue-500);
  --color-primary-hover: var(--color-blue-600);
  --color-primary-active: var(--color-blue-700);
  --color-secondary: var(--color-slate-100);
  --color-secondary-hover: var(--color-slate-200);
  --color-secondary-active: var(--color-slate-300);
  --color-border: var(--color-border-default);
  --color-btn-primary-text: var(--color-white);
  --color-card-border: var(--color-border-subtle);
  --color-card-border-inner: var(--color-border-subtle);
  --color-error: var(--color-red-500);
  --color-success: var(--color-green-500);
  --color-warning: var(--color-amber-500);
  --color-info: var(--color-slate-500);
  --color-focus-ring: rgba(var(--color-teal-500-rgb), 0.4);

  /* RGB versions for light mode */
  --color-success-rgb: var(--color-teal-500-rgb);
  --color-error-rgb: var(--color-red-500-rgb);
  --color-warning-rgb: var(--color-orange-500-rgb);
  --color-info-rgb: var(--color-slate-500-rgb);
}

/* Base styles */
html {
  font-size: var(--font-size-base);
  font-family: var(--font-family-base);
  line-height: var(--line-height-normal);
  color: var(--color-text-primary);
  background-color: var(--color-background);
  -webkit-font-smoothing: antialiased;
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 0;
  background: var(--color-background);
  color: var(--color-text-primary);
  font-family: var(--font-family-base);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

*,
*::before,
*::after {
  box-sizing: inherit;
}

/* Typography */
h1,
h2,
h3,
h4,
h5,
h6 {
  margin: 0;
  font-weight: var(--font-weight-semibold);
  line-height: var(--line-height-tight);
  color: var(--color-text-primary);
  letter-spacing: var(--letter-spacing-tight);
}

h1 {
  font-size: var(--font-size-4xl);
}
h2 {
  font-size: var(--font-size-3xl);
}
h3 {
  font-size: var(--font-size-2xl);
}
h4 {
  font-size: var(--font-size-xl);
}
h5 {
  font-size: var(--font-size-lg);
}
h6 {
  font-size: var(--font-size-md);
}

p {
  margin: 0 0 var(--space-16) 0;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-standard);
}

a:hover {
  color: var(--color-primary-hover);
}

code,
pre {
  font-family: var(--font-family-mono);
  font-size: calc(var(--font-size-base) * 0.95);
  background-color: var(--color-secondary);
  border-radius: var(--radius-sm);
}

code {
  padding: var(--space-1) var(--space-4);
}

pre {
  padding: var(--space-16);
  margin: var(--space-16) 0;
  overflow: auto;
  border: 1px solid var(--color-border);
}

pre code {
  background: none;
  padding: 0;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-8) var(--space-16);
  border-radius: var(--radius-base);
  font-size: var(--font-size-base);
  font-weight: 500;
  line-height: 1.5;
  cursor: pointer;
  transition: all var(--duration-normal) var(--ease-standard);
  border: none;
  text-decoration: none;
  position: relative;
}

.btn:focus-visible {
  outline: none;
  box-shadow: 0 0 0 3px var(--color-focus-ring);
}

.btn--primary {
  background: var(--color-primary);
  color: var(--color-white);
  border: 1px solid var(--color-primary);
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
  transition: all var(--duration-normal);
}

.btn--primary:hover {
  background: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

.btn--primary:active {
  background: var(--color-primary-active);
  border-color: var(--color-primary-active);
  box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
}

.btn--secondary {
  background: var(--color-white);
  color: var(--color-text-primary);
  border: 1px solid var(--color-border-default);
  transition: all var(--duration-normal);
}

.btn--secondary:hover {
  background: var(--color-slate-50);
  border-color: var(--color-border-emphasis);
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
}

.btn--secondary:active {
  background: var(--color-slate-100);
}

.btn--outline {
  background: transparent;
  border: 1px solid var(--color-primary);
  color: var(--color-primary);
  transition: all var(--duration-normal);
}

.btn--outline:hover {
  background: var(--color-blue-50);
  border-color: var(--color-primary-hover);
  color: var(--color-primary-hover);
}

.btn--sm {
  padding: var(--space-4) var(--space-12);
  font-size: var(--font-size-sm);
  border-radius: var(--radius-sm);
}

.btn--lg {
  padding: var(--space-10) var(--space-20);
  font-size: var(--font-size-lg);
  border-radius: var(--radius-md);
}

.btn--full-width {
  width: 100%;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Form elements */
.form-control {
  display: block;
  width: 100%;
  padding: var(--space-8) var(--space-12);
  font-size: var(--font-size-md);
  line-height: 1.5;
  color: var(--color-text-primary);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-base);
  transition: border-color var(--duration-fast) var(--ease-standard),
    box-shadow var(--duration-fast) var(--ease-standard);
}

textarea.form-control {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
}

select.form-control {
  padding: var(--space-8) var(--space-12);
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  background-image: var(--select-caret-light);
  background-repeat: no-repeat;
  background-position: right var(--space-12) center;
  background-size: 16px;
  padding-right: var(--space-32);
}

/* Add a dark mode specific caret */
@media (prefers-color-scheme: dark) {
  select.form-control {
    background-image: var(--select-caret-dark);
  }
}

/* Also handle data-color-scheme */
[data-color-scheme="dark"] select.form-control {
  background-image: var(--select-caret-dark);
}

[data-color-scheme="light"] select.form-control {
  background-image: var(--select-caret-light);
}

.form-control:focus {
  border-color: var(--color-primary);
  outline: var(--focus-outline);
}

.form-label {
  display: block;
  margin-bottom: var(--space-8);
  font-weight: var(--font-weight-medium);
  font-size: var(--font-size-sm);
}

.form-group {
  margin-bottom: var(--space-16);
}

/* Card component */
.card {
  background-color: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-card-border);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: box-shadow var(--duration-normal) var(--ease-standard);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

.card__body {
  padding: var(--space-16);
}

.card__header,
.card__footer {
  padding: var(--space-16);
  border-bottom: 1px solid var(--color-card-border-inner);
}

/* Status indicators - simplified with CSS variables */
.status {
  display: inline-flex;
  align-items: center;
  padding: var(--space-6) var(--space-12);
  border-radius: var(--radius-full);
  font-weight: var(--font-weight-medium);
  font-size: var(--font-size-sm);
}

.status--success {
  background-color: rgba(
    var(--color-success-rgb, 33, 128, 141),
    var(--status-bg-opacity)
  );
  color: var(--color-success);
  border: 1px solid
    rgba(var(--color-success-rgb, 33, 128, 141), var(--status-border-opacity));
}

.status--error {
  background-color: rgba(
    var(--color-error-rgb, 192, 21, 47),
    var(--status-bg-opacity)
  );
  color: var(--color-error);
  border: 1px solid
    rgba(var(--color-error-rgb, 192, 21, 47), var(--status-border-opacity));
}

.status--warning {
  background-color: rgba(
    var(--color-warning-rgb, 168, 75, 47),
    var(--status-bg-opacity)
  );
  color: var(--color-warning);
  border: 1px solid
    rgba(var(--color-warning-rgb, 168, 75, 47), var(--status-border-opacity));
}

.status--info {
  background-color: rgba(
    var(--color-info-rgb, 98, 108, 113),
    var(--status-bg-opacity)
  );
  color: var(--color-info);
  border: 1px solid
    rgba(var(--color-info-rgb, 98, 108, 113), var(--status-border-opacity));
}

/* Container layout */
.container {
  width: 100%;
  margin-right: auto;
  margin-left: auto;
  padding-right: var(--space-16);
  padding-left: var(--space-16);
}

@media (min-width: 640px) {
  .container {
    max-width: var(--container-sm);
  }
}
@media (min-width: 768px) {
  .container {
    max-width: var(--container-md);
  }
}
@media (min-width: 1024px) {
  .container {
    max-width: var(--container-lg);
  }
}
@media (min-width: 1280px) {
  .container {
    max-width: var(--container-xl);
  }
}

/* Utility classes */
.flex {
  display: flex;
}
.flex-col {
  flex-direction: column;
}
.items-center {
  align-items: center;
}
.justify-center {
  justify-content: center;
}
.justify-between {
  justify-content: space-between;
}
.gap-4 {
  gap: var(--space-4);
}
.gap-8 {
  gap: var(--space-8);
}
.gap-16 {
  gap: var(--space-16);
}

.m-0 {
  margin: 0;
}
.mt-8 {
  margin-top: var(--space-8);
}
.mb-8 {
  margin-bottom: var(--space-8);
}
.mx-8 {
  margin-left: var(--space-8);
  margin-right: var(--space-8);
}
.my-8 {
  margin-top: var(--space-8);
  margin-bottom: var(--space-8);
}

.p-0 {
  padding: 0;
}
.py-8 {
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
}
.px-8 {
  padding-left: var(--space-8);
  padding-right: var(--space-8);
}
.py-16 {
  padding-top: var(--space-16);
  padding-bottom: var(--space-16);
}
.px-16 {
  padding-left: var(--space-16);
  padding-right: var(--space-16);
}

.block {
  display: block;
}
.hidden {
  display: none;
}

/* Accessibility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

:focus-visible {
  outline: var(--focus-outline);
  outline-offset: 2px;
}

/* Dark mode specifics */
[data-color-scheme="dark"] .btn--outline {
  border: 1px solid var(--color-border-secondary);
}

@font-face {
  font-family: 'FKGroteskNeue';
  src: url('https://r2cdn.perplexity.ai/fonts/FKGroteskNeue.woff2')
    format('woff2');
}

/* END PERPLEXITY DESIGN SYSTEM */
/* Custom styles for Literature Review Management System */

/* Header Styles - Academic Professional */
.header {
  background: var(--color-white);
  border-bottom: 1px solid var(--color-border-subtle);
  padding: var(--space-20) 0;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-24);
  flex-wrap: wrap;
}

.header-title {
  font-size: var(--font-size-3xl);
  color: var(--color-text-primary);
  margin: 0;
  flex-shrink: 0;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.header-search {
  display: flex;
  align-items: center;
  gap: var(--space-12);
  flex: 1;
  max-width: 500px;
}

.search-input {
  flex: 1;
  min-width: 300px;
  border-radius: var(--radius-full);
  background: rgba(var(--color-white), 0.8);
  border: 2px solid transparent;
  transition: all var(--duration-normal);
}

.search-input:focus {
  border-color: var(--color-primary);
  background: var(--color-white);
  box-shadow: 0 0 0 3px var(--color-focus-ring);
}

.search-btn {
  border-radius: var(--radius-full);
  padding: var(--space-10) var(--space-20);
  background: var(--color-primary);
  color: var(--color-white);
  border: none;
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
  transition: all var(--duration-normal);
  cursor: pointer;
}

.search-btn:hover {
  background: var(--color-primary-hover);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

.header-actions {
  display: flex;
  gap: var(--space-12);
  flex-shrink: 0;
  margin-left: auto;
}

/* Main Layout */
.main-layout {
  display: flex;
  flex-direction: column;
  min-height: calc(100vh - 120px);
  max-width: 100%;
}

/* Category Navigation - Enhanced */
.category-nav {
  background: linear-gradient(135deg, rgba(var(--color-white), 0.9) 0%, rgba(var(--color-cream-100), 0.9) 100%);
  border-bottom: 1px solid rgba(var(--color-dusty-rose-rgb), 0.15);
  padding: var(--space-24) var(--space-24);
  position: sticky;
  top: 100px;
  z-index: 50;
  backdrop-filter: blur(8px);
}

.category-tabs {
  display: flex;
  gap: var(--space-6);
  margin-bottom: var(--space-20);
  overflow-x: auto;
  padding-bottom: var(--space-8);
}

.category-tab {
  background: var(--color-white);
  border: 1px solid var(--color-border-default);
  padding: var(--space-12) var(--space-24);
  border-radius: var(--radius-full);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--duration-normal);
  font-weight: 500;
  white-space: nowrap;
  font-size: var(--font-size-sm);
  position: relative;
  overflow: hidden;
}

.category-tab::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(59, 130, 246, 0.1), transparent);
  transition: left 0.6s ease;
}

.category-tab:hover::before {
  left: 100%;
}

.category-tab.active {
  background: var(--color-primary);
  color: var(--color-white);
  border-color: var(--color-primary);
  box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.1);
}

.category-tab:hover:not(.active) {
  background: var(--color-blue-50);
  color: var(--color-primary);
  border-color: var(--color-primary);
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
}

.stats-summary {
  display: flex;
  gap: var(--space-32);
  align-items: center;
}

.stats-summary .stats-item {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.stats-summary .stats-label {
  color: var(--color-mauve);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
}

.stats-summary .stats-value {
  font-weight: var(--font-weight-bold);
  color: var(--color-rose-500);
  font-size: var(--font-size-lg);
}

/* Content Area */
.content-area {
  display: flex;
  gap: var(--space-24);
  padding: var(--space-24);
  flex: 1;
}

/* Main Content */
.main-content {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
}

/* Sort Bar */
.sort-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-24);
  padding: var(--space-16);
  background: var(--color-surface);
  border-radius: var(--radius-base);
  border: 1px solid var(--color-card-border);
}

.sort-controls {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.sort-controls label {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  white-space: nowrap;
  font-weight: var(--font-weight-medium);
}

.sort-select {
  min-width: 150px;
  font-size: var(--font-size-sm);
}

/* Delete Controls */
.delete-controls {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.delete-controls .btn {
  font-size: var(--font-size-sm);
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.delete-controls .btn span {
  font-size: var(--font-size-xs);
}

.view-info {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
}

/* Papers Grid */
.papers-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-24);
  margin-bottom: var(--space-32);
  width: 100%;
}

/* Paper Card - Enhanced Movie Style */
.paper-card {
  background: var(--color-white);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
  transition: all var(--duration-normal);
  cursor: pointer;
  position: relative;
  height: 480px;
  display: flex;
  flex-direction: column;
  border: 1px solid var(--color-border-subtle);
}

.paper-card:hover {
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  border-color: var(--color-border-default);
}

.paper-card-header {
  height: 300px;
  background: var(--color-slate-50);
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-16);
  flex-shrink: 0;
  overflow: hidden;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

/* Paper Selection Checkbox */
.paper-select-container {
  position: absolute;
  top: var(--space-8);
  left: var(--space-8);
  z-index: 3;
}

.paper-select-checkbox {
  width: 20px;
  height: 20px;
  accent-color: var(--color-primary);
  cursor: pointer;
  border-radius: var(--radius-sm);
}

/* Paper Delete Button */
.paper-delete-btn {
  position: absolute;
  top: var(--space-8);
  right: var(--space-8);
  z-index: 3;
  width: 32px;
  height: 32px;
  background: rgba(239, 68, 68, 0.9);
  color: white;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  transition: all var(--duration-normal);
  backdrop-filter: blur(4px);
}

.paper-card:hover .paper-delete-btn {
  opacity: 1;
}

.paper-delete-btn:hover {
  background: rgba(220, 38, 38, 0.95);
  transform: scale(1.1);
}

.paper-delete-btn span {
  font-size: 14px;
}

.paper-image-container {
  position: relative;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 2;
}

.image-overlay {
  position: absolute;
  top: var(--space-12);
  right: var(--space-12);
  width: 36px;
  height: 36px;
  background: rgba(var(--color-rose-500-rgb), 0.9);
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: all var(--duration-normal);
  cursor: pointer;
  z-index: 3;
  backdrop-filter: blur(8px);
}

.paper-card:hover .image-overlay {
  opacity: 1;
  transform: scale(1.1);
}

.overlay-icon {
  color: var(--color-white);
  font-size: var(--font-size-base);
}

.image-overlay:hover {
  background: rgba(var(--color-rose-600-rgb), 0.95);
  transform: scale(1.2);
}

/* Image Manager Modal Styles */
.current-image-section {
  margin-bottom: var(--space-24);
}

.current-image-section h4 {
  margin-bottom: var(--space-12);
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
}

.current-image-container {
  width: 200px;
  height: 150px;
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-base);
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-secondary);
  margin: 0 auto;
}

.current-image-preview {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: var(--radius-base);
}

.current-image-placeholder {
  text-align: center;
}

.current-image-placeholder span {
  font-size: 48px;
  color: var(--color-text-secondary);
}

.image-actions {
  display: flex;
  gap: var(--space-24);
  flex-wrap: wrap;
}

.action-group {
  flex: 1;
  min-width: 250px;
}

.action-group h4 {
  margin-bottom: var(--space-12);
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
}

.upload-area-small {
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-base);
  padding: var(--space-20);
  text-align: center;
  background: var(--color-secondary);
  cursor: pointer;
  transition: all var(--duration-normal);
}

.upload-area-small:hover,
.upload-area-small.drag-over {
  border-color: var(--color-primary);
  background: rgba(var(--color-teal-500-rgb), 0.1);
}

.upload-icon-small {
  font-size: 32px;
  margin-bottom: var(--space-8);
}

.upload-text-small {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--space-4);
  color: var(--color-text-primary);
}

.upload-hint-small {
  font-size: var(--font-size-xs);
  color: var(--color-text-secondary);
  margin: 0;
}

.button-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
}

.button-group .btn {
  justify-content: center;
}

.paper-icon {
  font-size: 80px;
  opacity: 0.8;
  color: var(--color-primary);
}

.paper-thumbnail {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: var(--radius-sm);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
  transition: opacity var(--duration-normal);
}

.paper-thumbnail:hover {
  opacity: 0.95;
}

/* Loading state for thumbnails */
.paper-card-header {
  position: relative;
}

.paper-card-header::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
  transform: translateX(-100%);
  animation: shimmer 1.5s infinite;
  display: none;
}

.paper-card.loading .paper-card-header::after {
  display: block;
}

@keyframes shimmer {
  100% {
    transform: translateX(100%);
  }
}

.paper-card-content {
  padding: var(--space-16);
  height: 160px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  flex: 1;
  position: relative;
  z-index: 2;
  background: rgba(var(--color-white), 0.95);
}

.paper-card-title {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-slate-900);
  margin: 0 0 var(--space-8) 0;
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
  height: 4.2em;
}

.paper-card-meta {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  flex: 1;
}

.paper-card-authors {
  color: var(--color-mauve);
  font-size: var(--font-size-xs);
  display: -webkit-box;
  -webkit-line-clamp: 1;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.paper-card-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: auto;
}

.paper-card-venue {
  color: var(--color-rose-500);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  flex: 1;
  margin-right: var(--space-8);
  display: -webkit-box;
  -webkit-line-clamp: 1;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.paper-card-year {
  color: var(--color-mauve);
  font-size: var(--font-size-xs);
  background: rgba(var(--color-dusty-rose-rgb), 0.15);
  padding: var(--space-2) var(--space-8);
  border-radius: var(--radius-full);
  flex-shrink: 0;
  border: 1px solid rgba(var(--color-dusty-rose-rgb), 0.2);
}

.paper-card-stats {
  display: flex;
  gap: var(--space-16);
  margin-top: var(--space-6);
}

.paper-stat {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  color: var(--color-mauve);
  font-size: var(--font-size-xs);
}

.paper-stat-icon {
  font-size: var(--font-size-sm);
}

/* Right Sidebar Filters - Enhanced */
.filters-sidebar {
  width: 280px;
  flex-shrink: 0;
  background: var(--color-white);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border-subtle);
  padding: var(--space-24);
  height: fit-content;
  position: sticky;
  top: 200px;
  max-height: calc(100vh - 220px);
  overflow-y: auto;
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
}

.filters-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-24);
  padding-bottom: var(--space-20);
  border-bottom: 1px solid var(--color-border-subtle);
}

.filters-header h3 {
  margin: 0;
  font-size: var(--font-size-lg);
  color: var(--color-text-primary);
  font-weight: 600;
}

.reset-filters {
  background: var(--color-white);
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
  border-radius: var(--radius-full);
  transition: all var(--duration-normal);
  padding: var(--space-6) var(--space-12);
  font-size: var(--font-size-sm);
}

.reset-filters:hover {
  background: var(--color-blue-50);
  border-color: var(--color-primary-hover);
  color: var(--color-primary-hover);
}

/* Remove old sidebar styles and update existing ones */

.filter-group {
  margin-bottom: var(--space-24);
  padding: var(--space-16);
  background: var(--color-slate-50);
  border-radius: var(--radius-base);
  border: 1px solid var(--color-border-subtle);
}

.filter-label {
  display: block;
  font-weight: 600;
  margin-bottom: var(--space-12);
  color: var(--color-text-primary);
  font-size: var(--font-size-sm);
}

/* Year Filter - Professional Academic Style */
.year-filter {
  display: flex;
  flex-direction: column;
  gap: var(--space-12);
}

.year-slider {
  width: 100%;
  height: 8px;
  background: var(--color-slate-200);
  border-radius: var(--radius-full);
  outline: none;
  -webkit-appearance: none;
  position: relative;
  cursor: pointer;
  margin: var(--space-8) 0;
}

.year-slider::-webkit-slider-thumb {
  appearance: none;
  width: 20px;
  height: 20px;
  background: var(--color-primary);
  border: 2px solid var(--color-white);
  border-radius: 50%;
  cursor: pointer;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  transition: all var(--duration-normal);
}

.year-slider::-webkit-slider-thumb:hover {
  background: var(--color-primary-hover);
  transform: scale(1.1);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

.year-slider::-moz-range-thumb {
  width: 20px;
  height: 20px;
  background: var(--color-primary);
  border: 2px solid var(--color-white);
  border-radius: 50%;
  cursor: pointer;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  border: none;
}

.year-slider:focus {
  box-shadow: 0 0 0 3px var(--color-focus-ring);
}

.year-display {
  text-align: center;
  font-weight: 600;
  color: var(--color-text-primary);
  font-size: var(--font-size-base);
  padding: var(--space-12);
  background: var(--color-slate-50);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-base);
  margin-top: var(--space-8);
  font-family: var(--font-family-mono);
  letter-spacing: 0.5px;
  user-select: none;
}

.year-display span {
  font-weight: 700;
  color: var(--color-primary);
}

/* Checkbox Groups - Enhanced */
.checkbox-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
  max-height: 200px;
  overflow-y: auto;
}

.checkbox-item {
  display: flex;
  align-items: center;
  gap: var(--space-12);
  padding: var(--space-8);
  border-radius: var(--radius-base);
  transition: all var(--duration-normal);
  background: rgba(var(--color-white), 0.6);
  border: 1px solid rgba(var(--color-dusty-rose-rgb), 0.1);
}

.checkbox-item:hover {
  background: rgba(var(--color-rose-500-rgb), 0.05);
  border-color: rgba(var(--color-rose-500-rgb), 0.2);
  transform: translateX(2px);
}

.checkbox-item input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--color-rose-500);
  border-radius: var(--radius-sm);
}

.checkbox-item label {
  flex: 1;
  font-size: var(--font-size-sm);
  cursor: pointer;
  margin: 0;
  color: var(--color-slate-900);
  font-weight: var(--font-weight-medium);
}

.item-count {
  font-size: var(--font-size-xs);
  color: var(--color-rose-500);
  background: rgba(var(--color-rose-500-rgb), 0.1);
  padding: var(--space-2) var(--space-8);
  border-radius: var(--radius-full);
  min-width: 24px;
  text-align: center;
  font-weight: var(--font-weight-bold);
  border: 1px solid rgba(var(--color-rose-500-rgb), 0.2);
}

/* Citation Filter */
.citation-filter {
  display: flex;
  gap: var(--space-8);
}

.citation-input {
  flex: 1;
  font-size: var(--font-size-sm);
  padding: var(--space-6) var(--space-8);
}

/* Main Content */
.main-content {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
}

/* Statistics Bar */
.stats-bar {
  display: flex;
  gap: var(--space-32);
  background-color: var(--color-surface);
  padding: var(--space-16) var(--space-20);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-card-border);
  margin-bottom: var(--space-24);
  flex-wrap: wrap;
}

.stats-item {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.stats-label {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
}

.stats-value {
  font-weight: var(--font-weight-bold);
  color: var(--color-primary);
  font-size: var(--font-size-lg);
}

/* View Controls */
.view-controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-24);
  flex-wrap: wrap;
  gap: var(--space-16);
  background-color: var(--color-surface);
  padding: var(--space-16);
  border-radius: var(--radius-base);
  border: 1px solid var(--color-card-border);
}

.view-toggle {
  display: flex;
  gap: var(--space-4);
  background: var(--color-secondary);
  padding: var(--space-4);
  border-radius: var(--radius-base);
}

.view-btn {
  border: none;
  background: transparent;
  padding: var(--space-8) var(--space-16);
  border-radius: var(--radius-sm);
  transition: all var(--duration-fast);
  color: var(--color-text-primary);
  cursor: pointer;
  font-size: var(--font-size-sm);
}

.view-btn.active {
  background: var(--color-primary);
  color: var(--color-btn-primary-text);
}

.view-btn:hover:not(.active) {
  background: var(--color-secondary-hover);
}

.sort-controls {
  display: flex;
  align-items: center;
  gap: var(--space-8);
}

.sort-controls label {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  white-space: nowrap;
}

.sort-select {
  min-width: 180px;
  font-size: var(--font-size-sm);
}

/* Results Container */
.results-container {
  flex: 1;
  min-height: 200px;
}

/* Paper Cards */
.papers-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-16);
}

.papers-list.grid-view {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
  gap: var(--space-20);
}

.paper-card {
  background: var(--color-surface);
  border: 1px solid var(--color-card-border);
  border-radius: var(--radius-lg);
  padding: var(--space-20);
  transition: all var(--duration-normal);
  cursor: pointer;
}

.paper-card:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.paper-header {
  margin-bottom: var(--space-12);
}

.paper-title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  margin: 0 0 var(--space-8) 0;
  color: var(--color-text-primary);
  line-height: 1.3;
}

.paper-authors {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  margin-bottom: var(--space-4);
}

.paper-venue {
  color: var(--color-primary);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
}

.paper-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-12);
  margin-bottom: var(--space-12);
}

.meta-item {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  font-size: var(--font-size-xs);
  color: var(--color-text-secondary);
}

.paper-keywords {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-6);
  margin-top: var(--space-12);
}

.keyword-tag {
  background: var(--color-bg-1);
  color: var(--color-primary);
  padding: var(--space-4) var(--space-8);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
}

/* Timeline View */
.timeline-view {
  padding: var(--space-24);
}

.timeline-view.hidden {
  display: none;
}

.timeline-year {
  margin-bottom: var(--space-32);
}

.timeline-year-label {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  color: var(--color-primary);
  margin-bottom: var(--space-16);
  padding-bottom: var(--space-8);
  border-bottom: 2px solid var(--color-primary);
}

.timeline-papers {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--space-16);
  padding-left: var(--space-20);
}

/* Modal Styles */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  backdrop-filter: blur(4px);
}

.modal.hidden {
  display: none;
}

.modal-content {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  max-width: 90vw;
  max-height: 90vh;
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-20);
  border-bottom: 1px solid var(--color-border);
}

.modal-header h3 {
  margin: 0;
  color: var(--color-text-primary);
}

.modal-close {
  background: none;
  border: none;
  font-size: var(--font-size-3xl);
  color: var(--color-text-secondary);
  cursor: pointer;
  padding: var(--space-4);
  line-height: 1;
}

.modal-close:hover {
  color: var(--color-text-primary);
}

.modal-body {
  padding: var(--space-20);
  overflow-y: auto;
  max-height: calc(90vh - 80px);
}

/* Chart Tabs */
.chart-tabs {
  display: flex;
  gap: var(--space-4);
  margin-bottom: var(--space-20);
  border-bottom: 1px solid var(--color-border);
}

.chart-tab {
  background: none;
  border: none;
  padding: var(--space-12) var(--space-16);
  border-bottom: 2px solid transparent;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--duration-fast);
  font-weight: var(--font-weight-medium);
}

.chart-tab.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.chart-tab:hover {
  color: var(--color-text-primary);
}

/* PDF Viewer Modal Styles */
.pdf-viewer-content {
  width: 95vw;
  max-width: 1200px;
  height: 90vh;
  max-height: 800px;
}

.pdf-viewer-content .modal-header {
  display: flex;
  align-items: center;
  gap: var(--space-16);
  padding: var(--space-16) var(--space-20);
  border-bottom: 2px solid rgba(var(--color-dusty-rose-rgb), 0.15);
  background: linear-gradient(135deg, var(--color-cream-100), var(--color-warm-50));
}

.pdf-viewer-controls {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  flex: 1;
  justify-content: center;
}

.pdf-page-info {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  font-weight: var(--font-weight-medium);
  color: var(--color-slate-900);
}

.pdf-page-input {
  width: 60px;
  text-align: center;
  padding: var(--space-4) var(--space-6);
  border-radius: var(--radius-sm);
  border: 1px solid rgba(var(--color-dusty-rose-rgb), 0.3);
  font-size: var(--font-size-sm);
}

.pdf-zoom-info {
  min-width: 50px;
  text-align: center;
  font-weight: var(--font-weight-medium);
  color: var(--color-rose-500);
  font-size: var(--font-size-sm);
}

.pdf-viewer-body {
  height: calc(90vh - 120px);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: auto;
  background: linear-gradient(135deg, 
    rgba(var(--color-cream-50), 0.8), 
    rgba(var(--color-warm-50), 0.8));
}

.pdf-canvas {
  max-width: 100%;
  max-height: 100%;
  border-radius: var(--radius-base);
  box-shadow: 0 8px 32px rgba(var(--color-slate-900-rgb), 0.15);
  transition: transform var(--duration-normal);
}

.pdf-loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-16);
  color: var(--color-rose-500);
}

.loading-spinner {
  width: 48px;
  height: 48px;
  border: 4px solid rgba(var(--color-dusty-rose-rgb), 0.3);
  border-top: 4px solid var(--color-rose-500);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.pdf-error {
  text-align: center;
  color: var(--color-text-secondary);
  padding: var(--space-32);
}

.pdf-error h3 {
  color: var(--color-rose-500);
  margin-bottom: var(--space-16);
}

/* PDF Continuous Scroll Styles */
.pdf-scroll-container {
  width: 100%;
  height: 100%;
  overflow-y: auto;
  overflow-x: hidden;
  padding: var(--space-16);
}

.pdf-pages-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-16);
  max-width: 100%;
}

.pdf-page-wrapper {
  position: relative;
  background: var(--color-white);
  box-shadow: var(--shadow-lg);
  border-radius: var(--radius-base);
  padding: var(--space-8);
  margin-bottom: var(--space-16);
}

.pdf-page-canvas {
  display: block;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
}

.pdf-page-label {
  position: absolute;
  top: var(--space-4);
  right: var(--space-8);
  background: rgba(var(--color-slate-900-rgb), 0.8);
  color: var(--color-white);
  padding: var(--space-4) var(--space-8);
  border-radius: var(--radius-base);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
  z-index: 10;
}

/* Smooth scrolling for PDF container */
.pdf-scroll-container {
  scroll-behavior: smooth;
}

/* PDF Viewer - Fullscreen Mode */
.pdf-viewer-fullscreen {
  width: 100vw !important;
  height: 100vh !important;
  max-width: 100vw !important;
  max-height: 100vh !important;
  border-radius: 0 !important;
  margin: 0 !important;
}

.pdf-minimal-header {
  padding: var(--space-8) var(--space-16) !important;
  background: rgba(var(--color-slate-900-rgb), 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.pdf-minimal-header h3 {
  color: var(--color-white);
  font-size: var(--font-size-sm);
  margin: 0;
  flex: 1;
}

.pdf-minimal-header .modal-close {
  color: var(--color-white);
  background: rgba(255, 255, 255, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: var(--radius-full);
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  font-weight: bold;
  transition: all 0.2s ease;
  cursor: pointer;
  z-index: 1000;
}

.pdf-minimal-header .modal-close:hover {
  background: rgba(255, 255, 255, 0.2);
  transform: scale(1.1);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

.pdf-close-btn {
  position: relative;
}

.pdf-close-btn::before {
  content: '';
  position: absolute;
  top: -10px;
  right: -10px;
  bottom: -10px;
  left: -10px;
  background: transparent;
  border-radius: var(--radius-full);
}

/* Floating close button */
.pdf-floating-close {
  position: fixed;
  top: 20px;
  right: 20px;
  z-index: 10001;
}

.floating-close-btn {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-full);
  background: rgba(0, 0, 0, 0.8);
  color: var(--color-white);
  border: 2px solid rgba(255, 255, 255, 0.2);
  font-size: 20px;
  font-weight: bold;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.3s ease;
  backdrop-filter: blur(10px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.floating-close-btn:hover {
  background: rgba(255, 0, 0, 0.8);
  transform: scale(1.1);
  box-shadow: 0 6px 20px rgba(255, 0, 0, 0.4);
  border-color: rgba(255, 255, 255, 0.4);
}

.floating-close-btn:active {
  transform: scale(0.95);
}

.pdf-fullscreen-body {
  height: calc(100vh - 60px) !important;
  padding: 0 !important;
}

.pdf-viewer-fullscreen .pdf-scroll-container {
  padding: var(--space-8) !important;
  background: #f5f5f5;
}

.pdf-viewer-fullscreen .pdf-page-wrapper {
  background: var(--color-white);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  border-radius: var(--radius-base);
  padding: 0;
  margin-bottom: var(--space-12);
  overflow: hidden;
}

.pdf-viewer-fullscreen .pdf-page-canvas {
  width: 100%;
  height: auto;
  display: block;
}

.pdf-viewer-fullscreen .pdf-page-label {
  background: rgba(var(--color-slate-900-rgb), 0.7);
  color: var(--color-white);
  padding: var(--space-2) var(--space-8);
  font-size: var(--font-size-xs);
  position: absolute;
  top: var(--space-8);
  right: var(--space-8);
  border-radius: var(--radius-base);
  backdrop-filter: blur(5px);
}

.pdf-page-error {
  background: var(--color-white);
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-base);
  padding: var(--space-32);
  margin-bottom: var(--space-16);
  text-align: center;
  color: var(--color-text-secondary);
}

.pdf-page-error p {
  margin: 0;
  font-size: var(--font-size-sm);
}
}

/* Custom scrollbar for PDF container */
.pdf-scroll-container::-webkit-scrollbar {
  width: 8px;
}

.pdf-scroll-container::-webkit-scrollbar-track {
  background: var(--color-secondary);
  border-radius: var(--radius-base);
}

.pdf-scroll-container::-webkit-scrollbar-thumb {
  background: var(--color-text-secondary);
  border-radius: var(--radius-base);
}

.pdf-scroll-container::-webkit-scrollbar-thumb:hover {
  background: var(--color-primary);
}

/* Mobile responsive for PDF viewer */
@media (max-width: 768px) {
  .pdf-viewer-content {
    width: 100vw;
    height: 100vh;
    max-height: none;
    border-radius: 0;
  }
  
  .pdf-viewer-controls {
    flex-wrap: wrap;
    gap: var(--space-4);
  }
  
  .pdf-viewer-body {
    height: calc(100vh - 140px);
  }
  
  .pdf-scroll-container {
    padding: var(--space-8);
  }
  
  .pdf-page-wrapper {
    margin-bottom: var(--space-8);
    padding: var(--space-4);
  }
  
  .pdf-pages-container {
    gap: var(--space-8);
  }
}

/* Paper Details Layout - Enhanced Academic Style */
.paper-details-layout {
  display: flex;
  gap: var(--space-24);
  min-height: 400px;
}

.paper-details-image {
  flex-shrink: 0;
  width: 250px;
  height: 350px;
  border: 2px solid var(--color-border-default);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-surface);
}

.paper-details-thumbnail {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: var(--radius-base);
}

.paper-details-icon {
  font-size: 120px;
  opacity: 0.7;
  color: var(--color-primary);
}

.paper-details-content {
  flex: 1;
  min-width: 0;
}

/* Paper Details - Enhanced Visual Hierarchy */
.paper-details {
  display: flex;
  flex-direction: column;
  gap: var(--space-20);
}

.detail-section {
  border-bottom: 1px solid var(--color-border-subtle);
  padding-bottom: var(--space-16);
  margin-bottom: var(--space-4);
}

.detail-section:last-child {
  border-bottom: none;
  padding-bottom: 0;
  margin-bottom: 0;
}

/* Enhanced Label Styling for Better Contrast */
.detail-label {
  font-weight: var(--font-weight-bold);
  color: var(--color-slate-800);          /* Darker for better contrast */
  margin-bottom: var(--space-10);
  font-size: var(--font-size-base);       /* Slightly larger */
  text-transform: uppercase;              /* More formal academic style */
  letter-spacing: 0.5px;                  /* Better readability */
  border-left: 3px solid var(--color-primary);  /* Visual accent */
  padding-left: var(--space-12);         /* Space for accent */
  background: var(--color-slate-50);      /* Subtle background */
  padding-top: var(--space-6);
  padding-bottom: var(--space-6);
  border-radius: var(--radius-base);
}

/* Enhanced Value Styling */
.detail-value {
  color: var(--color-text-primary);       /* Darker text for better readability */
  line-height: 1.6;
  font-size: var(--font-size-base);       /* Consistent with label */
  padding-left: var(--space-15);          /* Align with label content */
  margin-top: var(--space-4);
}

/* Enhanced Link Buttons */
.detail-links {
  display: flex;
  gap: var(--space-12);
  flex-wrap: wrap;
  padding-left: var(--space-15);          /* Align with other content */
  margin-top: var(--space-8);
}

.detail-link {
  padding: var(--space-12) var(--space-20);
  border-radius: var(--radius-base);
  text-decoration: none;
  font-weight: var(--font-weight-semibold);
  transition: all var(--duration-fast);
  font-size: var(--font-size-base);
  border: 2px solid transparent;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: var(--space-8);
  text-align: center;
  min-height: 44px;                       /* Better touch target */
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.detail-link--primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-hover));
  color: var(--color-white);
  border-color: var(--color-primary);
}

.detail-link--primary:hover {
  background: linear-gradient(135deg, var(--color-primary-hover), var(--color-primary-active));
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(var(--color-blue-500-rgb), 0.3);
}

.detail-link--secondary {
  background: var(--color-surface-elevated);
  color: var(--color-text-primary);
  border-color: var(--color-border-emphasis);
}

.detail-link--secondary:hover {
  background: var(--color-slate-100);
  border-color: var(--color-primary);
  transform: translateY(-1px);
}

.detail-link--disabled {
  padding: var(--space-12) var(--space-20);
  border-radius: var(--radius-base);
  font-weight: var(--font-weight-medium);
  font-size: var(--font-size-base);
  background: var(--color-slate-100);
  color: var(--color-text-disabled);
  border: 2px solid var(--color-border-subtle);
  opacity: 0.7;
  cursor: not-allowed;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  gap: var(--space-8);
}

/* Paper Details Edit Mode - Enhanced */
.paper-details-actions {
  display: flex;
  justify-content: flex-end;
  gap: var(--space-12);
  margin-bottom: var(--space-20);
  padding: var(--space-16);
  border-bottom: 2px solid var(--color-border-default);
  background: var(--color-slate-50);
  border-radius: var(--radius-base);
}

.paper-details-actions .btn--sm {
  font-size: var(--font-size-base);
  padding: var(--space-10) var(--space-16);
  min-height: 40px;
  font-weight: var(--font-weight-semibold);
}

/* Enhanced Input Styling */
.detail-input, .detail-textarea {
  width: 100%;
  padding: var(--space-12) var(--space-16);
  border: 2px solid var(--color-border-default);
  border-radius: var(--radius-base);
  font-size: var(--font-size-base);
  background: var(--color-surface-elevated);
  color: var(--color-text-primary);
  transition: all 0.2s ease;
  margin-left: var(--space-15);            /* Align with content */
  margin-top: var(--space-8);
}

.detail-input:focus, .detail-textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(var(--color-blue-500-rgb), 0.15);
  background: var(--color-white);
}

.detail-textarea {
  resize: vertical;
  min-height: 100px;
  font-family: var(--font-family-base);
  line-height: var(--line-height-relaxed);
}

.detail-abstract {
  line-height: var(--line-height-relaxed);
  color: var(--color-text-primary);
  padding-left: var(--space-15);          /* Align with other content */
  margin-top: var(--space-8);
  font-size: var(--font-size-base);
}

/* Pagination */
.pagination {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: var(--space-8);
  margin-top: var(--space-32);
  padding: var(--space-16);
}

.pagination-btn {
  padding: var(--space-8) var(--space-12);
  border: 1px solid var(--color-border);
  background: var(--color-surface);
  color: var(--color-text-primary);
  border-radius: var(--radius-base);
  cursor: pointer;
  transition: all var(--duration-fast);
  font-size: var(--font-size-sm);
}

.pagination-btn:hover:not(:disabled) {
  background: var(--color-secondary);
  border-color: var(--color-primary);
}

.pagination-btn.active {
  background: var(--color-primary);
  color: var(--color-btn-primary-text);
  border-color: var(--color-primary);
}

.pagination-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.pagination-info {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin: 0 var(--space-16);
}

/* Utility Classes */
.hidden {
  display: none !important;
}

.visible {
  display: block;
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: var(--space-32);
  color: var(--color-text-secondary);
}

.empty-state h3 {
  margin-bottom: var(--space-16);
  color: var(--color-text-primary);
}

/* Responsive Design */
@media (max-width: 1024px) {
  .content-area {
    flex-direction: column;
    gap: var(--space-16);
  }
  
  .filters-sidebar {
    width: 100%;
    position: static;
    max-height: none;
  }
  
  .papers-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-20);
  }
  
  .category-tabs {
    justify-content: flex-start;
  }
  
  .stats-summary {
    gap: var(--space-16);
  }
}

@media (max-width: 768px) {
  .content-area {
    padding: var(--space-16);
  }
  
  .category-nav {
    padding: var(--space-16);
    top: 100px;
  }
  
  .header-content {
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-16);
  }
  
  .header-search {
    max-width: none;
  }
  
  .search-input {
    min-width: auto;
  }
  
  .header-actions {
    justify-content: center;
  }
  
  .sort-bar {
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-12);
  }
  
  .delete-controls {
    justify-content: center;
    margin-top: var(--space-8);
  }
  
  .delete-controls .btn {
    font-size: var(--font-size-xs);
    padding: var(--space-8) var(--space-12);
  }
  
  .stats-summary {
    flex-direction: column;
    gap: var(--space-8);
  }
  
  .papers-grid {
    grid-template-columns: 1fr;
  }
  
  .category-tabs {
    gap: var(--space-2);
  }
  
  .category-tab {
    padding: var(--space-8) var(--space-12);
    font-size: var(--font-size-xs);
  }
  
  /* Upload category selection mobile styles */
  .category-selection {
    grid-template-columns: 1fr;
    gap: var(--space-8);
  }
  
  .upload-modal-content {
    width: 95vw;
    max-width: none;
    margin: var(--space-16);
  }
  
  /* Paper details mobile layout */
  .paper-details-layout {
    flex-direction: column;
    gap: var(--space-16);
  }
  
  .paper-details-image {
    width: 100%;
    height: 200px;
    align-self: center;
    max-width: 300px;
  }
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: var(--space-32);
  color: var(--color-text-secondary);
}

.empty-state h3 {
  margin-bottom: var(--space-16);
  color: var(--color-text-primary);
}

/* Loading State */
.loading {
  text-align: center;
  padding: var(--space-32);
  color: var(--color-text-secondary);
}

/* Custom scrollbar */
.checkbox-group::-webkit-scrollbar,
.modal-body::-webkit-scrollbar,
.sidebar::-webkit-scrollbar {
  width: 6px;
}

.checkbox-group::-webkit-scrollbar-track,
.modal-body::-webkit-scrollbar-track,
.sidebar::-webkit-scrollbar-track {
  background: var(--color-secondary);
  border-radius: var(--radius-full);
}

.checkbox-group::-webkit-scrollbar-thumb,
.modal-body::-webkit-scrollbar-thumb,
.sidebar::-webkit-scrollbar-thumb {
  background: var(--color-primary);
  border-radius: var(--radius-full);
}

.checkbox-group::-webkit-scrollbar-thumb:hover,
.modal-body::-webkit-scrollbar-thumb:hover,
.sidebar::-webkit-scrollbar-thumb:hover {
  background: var(--color-primary-hover);
}

/* Upload Category Selection Styles */
.upload-category-section {
  margin-bottom: var(--space-24);
  padding: var(--space-16);
  background: rgba(var(--color-teal-500-rgb), 0.05);
  border-radius: var(--radius-base);
  border: 1px solid rgba(var(--color-teal-500-rgb), 0.2);
}

.upload-category-section h4 {
  margin-bottom: var(--space-16);
  color: var(--color-text-primary);
  font-weight: var(--font-weight-semibold);
  font-size: var(--font-size-lg);
}

.category-selection {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-12);
}

.category-option {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  padding: var(--space-8) var(--space-12);
  border-radius: var(--radius-base);
  transition: background-color var(--duration-fast);
  cursor: pointer;
}

.category-option:hover {
  background: var(--color-secondary);
}

.category-option input[type="radio"] {
  width: 18px;
  height: 18px;
  accent-color: var(--color-primary);
  margin: 0;
}

.category-option label {
  cursor: pointer;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-primary);
  margin: 0;
  flex: 1;
}

.category-option input[type="radio"]:checked + label {
  color: var(--color-primary);
  font-weight: var(--font-weight-semibold);
}

/* Upload Modal Styles */
.upload-modal-content {
  width: 90vw;
  max-width: 800px;
}

.upload-tabs {
  display: flex;
  gap: var(--space-4);
  margin-bottom: var(--space-20);
  border-bottom: 1px solid var(--color-border);
}

.upload-tab {
  background: none;
  border: none;
  padding: var(--space-12) var(--space-16);
  border-bottom: 2px solid transparent;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--duration-fast);
  font-weight: var(--font-weight-medium);
}

.upload-tab.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.upload-tab:hover {
  color: var(--color-text-primary);
}

.upload-tab-content {
  display: block;
}

.upload-tab-content.hidden {
  display: none;
}

/* File Upload Area */
.upload-area {
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-32);
  text-align: center;
  background: var(--color-secondary);
  transition: all var(--duration-normal);
  cursor: pointer;
}

.upload-area.drag-over {
  border-color: var(--color-primary);
  background: rgba(var(--color-teal-500-rgb), 0.1);
}

.upload-icon {
  font-size: 48px;
  margin-bottom: var(--space-16);
}

.upload-text {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--space-8);
  color: var(--color-text-primary);
}

.upload-hint {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-20);
}

/* Progress Bar */
.upload-progress {
  text-align: center;
  padding: var(--space-20);
}

.progress-bar {
  width: 100%;
  height: 8px;
  background: var(--color-secondary);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-bottom: var(--space-12);
}

.progress-fill {
  height: 100%;
  background: var(--color-primary);
  border-radius: var(--radius-full);
  transition: width var(--duration-normal);
  width: 0%;
}

.progress-text {
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  margin: 0;
}

/* Manual Entry Form */
.manual-entry-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-16);
}

.form-row {
  display: flex;
  gap: var(--space-16);
}

.form-row .form-group {
  flex: 1;
}

.form-actions {
  display: flex;
  justify-content: flex-end;
  gap: var(--space-12);
  padding-top: var(--space-16);
  border-top: 1px solid var(--color-border);
  margin-top: var(--space-8);
}

/* File List Styles */
.file-list {
  margin-top: var(--space-16);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-base);
  overflow: hidden;
}

.file-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-12) var(--space-16);
  border-bottom: 1px solid var(--color-border);
  background: var(--color-surface);
}

.file-item:last-child {
  border-bottom: none;
}

.file-info {
  display: flex;
  align-items: center;
  gap: var(--space-12);
  flex: 1;
}

.file-icon {
  font-size: var(--font-size-xl);
}

.file-details {
  flex: 1;
}

.file-name {
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--space-2);
  color: var(--color-text-primary);
  font-size: var(--font-size-sm);
}

.file-size {
  color: var(--color-text-secondary);
  font-size: var(--font-size-xs);
}

.file-status {
  padding: var(--space-4) var(--space-8);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-medium);
}

.file-status.success {
  background: rgba(var(--color-success-rgb), 0.2);
  color: var(--color-success);
}

.file-status.error {
  background: rgba(var(--color-error-rgb), 0.2);
  color: var(--color-error);
}

.file-status.processing {
  background: rgba(var(--color-warning-rgb), 0.2);
  color: var(--color-warning);
}

.remove-file {
  background: none;
  border: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  padding: var(--space-4);
  border-radius: var(--radius-sm);
  transition: color var(--duration-fast);
}

.remove-file:hover {
  color: var(--color-error);
}

/* Loading State */
.loading {
  text-align: center;
  padding: var(--space-32);
  color: var(--color-text-secondary);
}

/* Ensure proper display */
.papers-list:not(.hidden) {
  display: flex;
}

.papers-list.grid-view:not(.hidden) {
  display: grid;
}

/* Enhanced Category Selection for Batch Upload */
.upload-category-section {
  margin-bottom: var(--space-32);
  padding: var(--space-24);
  background: var(--color-slate-50);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border-subtle);
}

.upload-category-section h4 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0 0 var(--space-8) 0;
}

.category-help {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
  margin: 0 0 var(--space-24) 0;
  font-style: italic;
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-16);
  margin-bottom: var(--space-24);
}

.category-card {
  position: relative;
  background: var(--color-white);
  border: 2px solid var(--color-border-subtle);
  border-radius: var(--radius-base);
  overflow: hidden;
  transition: all var(--duration-normal);
  cursor: pointer;
}

.category-card:hover {
  border-color: var(--color-primary);
  box-shadow: 0 4px 12px rgba(var(--color-blue-500-rgb), 0.1);
  transform: translateY(-2px);
}

.category-card input[type="radio"] {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.category-card input[type="radio"]:checked + label {
  background: var(--color-blue-50);
  border-color: var(--color-primary);
}

.category-card input[type="radio"]:checked + label::after {
  content: '✓';
  position: absolute;
  top: var(--space-8);
  right: var(--space-12);
  width: 24px;
  height: 24px;
  background: var(--color-primary);
  color: var(--color-white);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 600;
}

.category-card label {
  display: flex;
  align-items: center;
  gap: var(--space-16);
  padding: var(--space-20);
  cursor: pointer;
  transition: all var(--duration-normal);
  height: 100%;
  border: none;
  background: none;
  position: relative;
}

.category-icon {
  font-size: 32px;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-slate-100);
  border-radius: var(--radius-base);
  flex-shrink: 0;
}

.category-info {
  flex: 1;
}

.category-info h5 {
  font-size: var(--font-size-base);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0 0 var(--space-4) 0;
}

.category-info p {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
  margin: 0;
  line-height: 1.4;
}

/* Selected Category Display */
.selected-category-display {
  padding: var(--space-16);
  background: var(--color-white);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-base);
  text-align: center;
}

.category-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-8);
  padding: var(--space-8) var(--space-16);
  background: var(--color-primary);
  color: var(--color-white);
  border-radius: var(--radius-full);
  font-weight: 600;
  font-size: var(--font-size-sm);
  margin-bottom: var(--space-8);
}

.badge-icon {
  font-size: 16px;
}

.category-description {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin: 0;
  font-style: italic;
}

/* Responsive Design for Category Cards */
@media (max-width: 768px) {
  .category-grid {
    grid-template-columns: 1fr;
  }
  
  .category-card label {
    padding: var(--space-16);
  }
  
  .category-icon {
    font-size: 24px;
    width: 40px;
    height: 40px;
  }
}

/* Upload Zone - Enhanced for Batch Operations */
.batch-upload-area {
  display: flex;
  flex-direction: column;
  gap: var(--space-24);
}

.upload-zone {
  border: 2px dashed var(--color-border-default);
  border-radius: var(--radius-lg);
  padding: var(--space-48) var(--space-24);
  text-align: center;
  background: var(--color-slate-50);
  transition: all var(--duration-normal);
  cursor: pointer;
}

.upload-zone:hover {
  border-color: var(--color-primary);
  background: var(--color-blue-50);
}

.upload-zone.drag-over {
  border-color: var(--color-primary);
  background: var(--color-blue-50);
  border-style: solid;
  transform: scale(1.02);
}

.upload-icon {
  font-size: 48px;
  margin-bottom: var(--space-16);
}

.upload-title {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0 0 var(--space-8) 0;
}

.upload-text {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin: 0 0 var(--space-8) 0;
}

.upload-hint {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
  margin: 0 0 var(--space-24) 0;
}

.upload-actions {
  display: flex;
  gap: var(--space-16);
  justify-content: center;
  flex-wrap: wrap;
}

.btn--lg {
  padding: var(--space-12) var(--space-24);
  font-size: var(--font-size-lg);
  border-radius: var(--radius-base);
}

.btn--lg span {
  margin-right: var(--space-8);
}

/* Batch Processing Panel */
.batch-panel {
  background: var(--color-white);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

.batch-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-20) var(--space-24);
  background: var(--color-slate-50);
  border-bottom: 1px solid var(--color-border-subtle);
}

.batch-info h4 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0 0 var(--space-4) 0;
}

.batch-info p {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
  margin: 0;
}

.batch-controls {
  display: flex;
  gap: var(--space-12);
  align-items: center;
}

/* File Queue */
.file-queue {
  max-height: 400px;
  overflow-y: auto;
  padding: var(--space-16);
}

.file-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-12) var(--space-16);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-base);
  margin-bottom: var(--space-8);
  background: var(--color-white);
  transition: all var(--duration-normal);
}

.file-item:hover {
  border-color: var(--color-border-default);
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
}

.file-item.processing {
  border-color: var(--color-primary);
  background: var(--color-blue-50);
}

.file-item.completed {
  border-color: var(--color-success);
  background: var(--color-success-bg);
}

.file-item.failed {
  border-color: var(--color-error);
  background: var(--color-error-bg);
}

.file-info {
  display: flex;
  align-items: center;
  gap: var(--space-12);
  flex: 1;
}

.file-icon {
  font-size: 24px;
  width: 32px;
  text-align: center;
}

.file-details h5 {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-primary);
  margin: 0 0 var(--space-2) 0;
  word-break: break-word;
}

.file-meta {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
  margin: 0;
}

.file-status {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  min-width: 120px;
  justify-content: flex-end;
}

.file-status-text {
  font-size: var(--font-size-sm);
  font-weight: 500;
}

.file-status.queued .file-status-text {
  color: var(--color-text-tertiary);
}

.file-status.processing .file-status-text {
  color: var(--color-primary);
}

.file-status.completed .file-status-text {
  color: var(--color-success);
}

.file-status.failed .file-status-text {
  color: var(--color-error);
}

.file-actions {
  display: flex;
  gap: var(--space-8);
}

.file-action-btn {
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-4);
  border-radius: var(--radius-sm);
  color: var(--color-text-tertiary);
  transition: all var(--duration-normal);
  font-size: 16px;
}

.file-action-btn:hover {
  background: var(--color-slate-100);
  color: var(--color-text-secondary);
}

.file-action-btn.retry {
  color: var(--color-primary);
}

.file-action-btn.remove {
  color: var(--color-error);
}

/* Batch Progress */
.batch-progress {
  padding: var(--space-20) var(--space-24);
  background: var(--color-slate-50);
  border-top: 1px solid var(--color-border-subtle);
}

.overall-progress {
  margin-bottom: var(--space-20);
}

.progress-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-8);
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text-primary);
}

.progress-bar {
  width: 100%;
  height: 12px;
  background: var(--color-slate-200);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-primary-hover));
  border-radius: var(--radius-full);
  transition: width var(--duration-normal);
  position: relative;
}

.progress-fill::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
  animation: shimmer 2s infinite;
}

/* GitHub Sync Progress Panel */
.github-sync-panel {
  margin-top: var(--space-16);
  padding: var(--space-20) var(--space-24);
  background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-lg);
}

.sync-header h5 {
  margin: 0 0 var(--space-8) 0;
  color: var(--color-primary);
  font-size: var(--font-size-lg);
  font-weight: 600;
}

.sync-warning {
  margin: 0;
  color: var(--color-warning);
  font-size: var(--font-size-sm);
  font-weight: 500;
  background: rgba(255, 193, 7, 0.1);
  padding: var(--space-8) var(--space-12);
  border-radius: var(--radius-sm);
  border-left: 4px solid var(--color-warning);
}

.sync-progress {
  margin: var(--space-16) 0;
}

.sync-progress-bar {
  width: 100%;
  height: 16px;
  background: rgba(255, 255, 255, 0.8);
  border-radius: var(--radius-full);
  overflow: hidden;
  border: 1px solid rgba(var(--color-primary-rgb), 0.2);
}

.sync-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-success));
  border-radius: var(--radius-full);
  transition: width var(--duration-slow);
  position: relative;
}

.sync-progress-fill::after {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.6), transparent);
  animation: shimmer 3s infinite;
}

.sync-status {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: var(--space-12);
}

.sync-status-text {
  color: var(--color-primary);
  font-weight: 500;
  font-size: var(--font-size-sm);
}

.sync-counter {
  background: var(--color-primary);
  color: white;
  padding: var(--space-4) var(--space-8);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-xs);
  font-weight: 600;
}

.sync-details {
  max-height: 200px;
  overflow-y: auto;
  margin-top: var(--space-16);
  border-top: 1px solid rgba(var(--color-primary-rgb), 0.2);
  padding-top: var(--space-12);
}

.sync-item {
  display: flex;
  align-items: center;
  gap: var(--space-8);
  padding: var(--space-6) 0;
  font-size: var(--font-size-sm);
}

.sync-item-status {
  width: 16px;
  height: 16px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 10px;
}

.sync-item-status.pending {
  background: var(--color-secondary);
  color: var(--color-text-secondary);
}

.sync-item-status.processing {
  background: var(--color-warning);
  color: white;
  animation: pulse 2s infinite;
}

.sync-item-status.completed {
  background: var(--color-success);
  color: white;
}

.sync-item-status.failed {
  background: var(--color-error);
  color: white;
}

.sync-item-text {
  flex: 1;
  color: var(--color-text-primary);
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

@keyframes shimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

/* Batch Status */
.batch-status {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: var(--space-16);
  margin-bottom: var(--space-20);
}

.status-item {
  text-align: center;
  padding: var(--space-12);
  background: var(--color-white);
  border-radius: var(--radius-base);
  border: 1px solid var(--color-border-subtle);
}

.status-label {
  display: block;
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
  margin-bottom: var(--space-4);
}

.status-count {
  display: block;
  font-size: var(--font-size-lg);
  font-weight: 700;
  color: var(--color-text-primary);
}

/* Batch Actions */
.batch-actions {
  display: flex;
  gap: var(--space-12);
  justify-content: center;
}

/* Status Indicators */
.status-indicator {
  display: inline-flex;
  align-items: center;
  gap: var(--space-4);
  font-size: var(--font-size-xs);
}

.status-indicator::before {
  content: '';
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-text-tertiary);
}

.status-indicator.queued::before {
  background: var(--color-text-tertiary);
}

.status-indicator.processing::before {
  background: var(--color-primary);
  animation: pulse 1.5s infinite;
}

.status-indicator.completed::before {
  background: var(--color-success);
}

.status-indicator.failed::before {
  background: var(--color-error);
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

/* Individual File Progress */
.file-progress {
  margin-top: var(--space-8);
  height: 4px;
  background: var(--color-slate-200);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.file-progress-fill {
  height: 100%;
  background: var(--color-primary);
  border-radius: var(--radius-full);
  transition: width var(--duration-normal);
}

/* Responsive Design */
@media (max-width: 768px) {
  .batch-header {
    flex-direction: column;
    gap: var(--space-16);
    align-items: stretch;
  }
  
  .batch-controls {
    justify-content: center;
  }
  
  .upload-actions {
    flex-direction: column;
    align-items: center;
  }
  
  .batch-status {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .batch-actions {
    flex-direction: column;
  }
}

/* Loading Animation for Processing Files */
.processing-spinner {
  display: inline-block;
  width: 16px;
  height: 16px;
  border: 2px solid var(--color-border-subtle);
  border-radius: 50%;
  border-top-color: var(--color-primary);
  animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* File size and compression info styles */
.size-info {
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.size-info.compressed {
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
}

.compression-info {
    color: var(--color-success);
    font-size: 12px;
    font-style: italic;
    display: block;
}

/* Processing status improvements */
.file-status-text {
    font-size: 13px;
    font-weight: 500;
}

/* File item status colors */
.file-item.processing {
    border-left: 4px solid var(--color-info);
    background: rgba(23, 162, 184, 0.05);
}

.file-item.completed {
    border-left: 4px solid var(--color-success);
    background: rgba(40, 167, 69, 0.05);
}

.file-item.failed {
    border-left: 4px solid var(--color-error);
    background: rgba(220, 53, 69, 0.05);
}

/* Parse warning styles */
.parse-warning {
    margin-top: 8px;
    padding: 6px 8px;
    background: rgba(255, 193, 7, 0.1);
    border: 1px solid rgba(255, 193, 7, 0.3);
    border-radius: 4px;
}

.parse-warning small {
    color: #856404;
    font-size: 11px;
    display: block;
}