@import url("https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Plus+Jakarta+Sans:wght@500;600;700;800&display=swap");

/* ===== DESIGN SYSTEM VARIABLES (Material 3 inspired) ===== */
:root {
  /* Colors */
  --color-surface: #f9f9ff;
  --color-surface-dim: #cfdaf2;
  --color-surface-bright: #f9f9ff;
  --color-surface-container-lowest: #ffffff;
  --color-surface-container-low: #f0f3ff;
  --color-surface-container: #e7eeff;
  --color-surface-container-high: #dee8ff;
  --color-surface-container-highest: #d8e3fb;
  --color-on-surface: #111c2d;
  --color-on-surface-variant: #434655;
  --color-inverse-surface: #263143;
  --color-inverse-on-surface: #ecf1ff;
  --color-outline: #737686;
  --color-outline-variant: #c3c6d7;
  --color-surface-tint: #0053db;
  
  --color-primary: #004ac6; /* Trust Blue core */
  --color-on-primary: #ffffff;
  --color-primary-container: #2563eb;
  --color-on-primary-container: #eeefff;
  --color-inverse-primary: #b4c5ff;
  
  --color-secondary: #006c49; /* Action Green core */
  --color-on-secondary: #ffffff;
  --color-secondary-container: #6cf8bb;
  --color-on-secondary-container: #00714d;
  
  --color-tertiary: #943700;
  --color-on-tertiary: #ffffff;
  --color-tertiary-container: #bc4800;
  --color-on-tertiary-container: #ffede6;
  
  --color-error: #ba1a1a;
  --color-on-error: #ffffff;
  --color-error-container: #ffdad6;
  --color-on-error-container: #93000a;

  --color-background: #f9f9ff;
  --color-on-background: #111c2d;

  /* Theme semantic mappings */
  --bg: var(--color-background);
  --surface: var(--color-surface-container-lowest);
  --text: var(--color-on-background);
  --text-muted: var(--color-on-surface-variant);
  --accent: var(--color-primary-container);
  --accent-soft: var(--color-on-primary-container);
  --border: var(--color-outline-variant);

  /* Spacing baseline rhythm */
  --spacing-base: 4px;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-gutter: 24px;

  /* Rounded Radii */
  --rounded-sm: 0.25rem;
  --rounded-default: 0.5rem;
  --rounded-md: 0.75rem;
  --rounded-lg: 1rem;
  --rounded-xl: 1.5rem;
  --rounded-full: 9999px;
  
  /* Fonts */
  --font-display: "Plus Jakarta Sans", sans-serif;
  --font-body: "Inter", sans-serif;
}

html.dark-mode {
  --color-surface: #111318;
  --color-surface-dim: #111c2d;
  --color-surface-bright: #263143;
  --color-surface-container-lowest: #0c0e12;
  --color-surface-container-low: #191b20;
  --color-surface-container: #212328;
  --color-surface-container-high: #2b2d33;
  --color-surface-container-highest: #36383f;
  --color-on-surface: #e2e2e9;
  --color-on-surface-variant: #c3c6d7;
  --color-inverse-surface: #f9f9ff;
  --color-inverse-on-surface: #111c2d;
  --color-outline: #8d90a0;
  --color-outline-variant: #434655;
  
  --color-primary: #b4c5ff;
  --color-on-primary: #00287a;
  --color-primary-container: #2563eb;
  --color-on-primary-container: #eff6ff;
  
  --color-secondary: #4edea3;
  --color-on-secondary: #003823;
  --color-secondary-container: #005236;
  --color-on-secondary-container: #6ffbbe;

  --color-background: #111318;
  --color-on-background: #e2e2e9;

  --bg: var(--color-background);
  --surface: var(--color-surface-container-low);
  --text: var(--color-on-background);
  --text-muted: var(--color-on-surface-variant);
  --accent: var(--color-primary);
  --accent-soft: rgba(37, 99, 235, 0.2);
  --border: var(--color-outline-variant);
}

/* ===== GENERAL RESET & BASE ===== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-body);
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.5;
  transition: background-color 0.25s ease, color 0.25s ease, border-color 0.25s ease;
}

/* ===== TYPOGRAPHY ===== */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  color: var(--text);
}

.text-display {
  font-family: var(--font-display);
  font-size: 48px;
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.02em;
}

.text-headline-lg {
  font-family: var(--font-display);
  font-size: 32px;
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.01em;
}

@media (max-width: 640px) {
  .text-headline-lg {
    font-size: 24px;
  }
}

.text-headline-md {
  font-family: var(--font-display);
  font-size: 24px;
  font-weight: 600;
  line-height: 1.3;
}

.text-headline-sm {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 600;
  line-height: 1.4;
}

.text-body-lg {
  font-family: var(--font-body);
  font-size: 18px;
  font-weight: 400;
  line-height: 1.6;
}

.text-body-md {
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.5;
}

.text-label-md {
  font-family: var(--font-body);
  font-size: 14px;
  font-weight: 500;
  line-height: 1;
  letter-spacing: 0.02em;
}

.text-code {
  font-family: monospace;
  font-size: 14px;
  font-weight: 400;
  line-height: 1.5;
}

/* ===== COMPONENT LAYOUTS & CONTAINERS ===== */
.max-width-grid {
  max-width: 1200px;
  margin: 0 auto;
  padding-left: var(--spacing-sm);
  padding-right: var(--spacing-sm);
}
@media (min-width: 1024px) {
  .max-width-grid {
    padding-left: var(--spacing-lg);
    padding-right: var(--spacing-lg);
  }
}

/* Elevation & Depth Layers */
.card {
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--rounded-md); /* 12px default */
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Level 1: Cards */
.card-level-1 {
  background-color: var(--color-surface-container-lowest);
  border: 1px solid var(--color-outline-variant);
  border-radius: 12px;
  box-shadow: none;
}

/* Level 2: Interactive Card */
.card-level-2 {
  background-color: var(--color-surface-container-lowest);
  border: 1px solid var(--color-outline-variant);
  border-radius: 12px;
  box-shadow: none;
}
.card-level-2:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px -2px rgba(0, 0, 0, 0.04), 0 2px 6px -1px rgba(0, 0, 0, 0.02);
  border-color: var(--color-primary-container);
}

/* Level 3: Overlays / Modals */
.card-level-3 {
  background-color: var(--color-surface-container-lowest);
  border: 1px solid var(--color-outline-variant);
  border-radius: 16px;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.08), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.text-muted {
  color: var(--text-muted);
}

.border-theme {
  border-color: var(--border);
}

/* ===== BUTTONS ===== */
.btn-primary {
  background-color: var(--color-primary);
  color: var(--color-on-primary) !important;
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: 8px; /* 0.5rem */
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all 0.2s ease;
  text-decoration: none;
}
.btn-primary:hover {
  background-color: var(--color-primary-container);
  transform: translateY(-1px);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.08);
}
.btn-primary:active {
  transform: translateY(0);
}

/* Legacy class compatibility */
.btn-accent {
  background-color: var(--color-primary-container);
  color: var(--color-on-primary) !important;
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all 0.2s ease;
  text-decoration: none;
}
.btn-accent:hover {
  background-color: var(--color-primary);
  transform: translateY(-1px);
}

.btn-secondary {
  background-color: transparent;
  color: var(--color-primary) !important;
  border: 1px solid var(--color-primary);
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all 0.2s ease;
  text-decoration: none;
}
.btn-secondary:hover {
  background-color: var(--color-surface-container-low);
  transform: translateY(-1px);
}

.btn-success {
  background-color: var(--color-secondary);
  color: var(--color-on-secondary) !important;
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all 0.2s ease;
  text-decoration: none;
}
.btn-success:hover {
  background-color: #007a53;
  transform: translateY(-1px);
}

/* ===== INPUTS ===== */
.input-field {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--color-outline-variant);
  border-radius: 8px;
  font-family: var(--font-body);
  font-size: 15px;
  background-color: var(--color-surface-container-lowest);
  color: var(--color-on-surface);
  transition: all 0.2s ease;
}
.input-field:focus {
  border-color: var(--color-primary);
  outline: none;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

/* ===== NAVIGATION & TABS ===== */
.nav-link {
  color: var(--color-on-surface-variant);
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 500;
  padding: 0.5rem 0.25rem;
  text-decoration: none;
  transition: color 0.2s ease;
  position: relative;
}
.nav-link:hover {
  color: var(--color-primary);
}
.nav-link.active {
  color: var(--color-primary);
  font-weight: 600;
}
.nav-link.active::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--color-primary);
  border-radius: 2px;
}

/* ===== PROGRESS PILLS / SYLLABUS PILLS ===== */
.pill {
  background-color: var(--color-surface-container-low);
  border: 1px solid var(--color-outline-variant);
  color: var(--color-on-surface-variant);
  font-size: 13px;
  font-weight: 500;
  padding: 0.5rem 1rem;
  border-radius: 9999px; /* Pill shape */
  cursor: pointer;
  transition: all 0.2s ease;
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}
.pill:hover {
  background-color: var(--color-surface-container-high);
  color: var(--color-primary);
  border-color: var(--color-primary);
}
.pill.active {
  background-color: var(--color-primary);
  color: var(--color-on-primary);
  border-color: var(--color-primary);
}

/* ===== PROGRESS INDICATORS ===== */
.progress-bar-container {
  height: 4px;
  background-color: var(--color-outline-variant);
  border-radius: 9999px;
  overflow: hidden;
}
.progress-bar-fill {
  height: 100%;
  background-color: var(--color-secondary); /* Action Green */
  border-radius: 9999px;
  transition: width 0.4s ease;
}

/* ===== EXAM QUESTION BLOCKS ===== */
.option-row {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem;
  border: 1px solid var(--color-outline-variant);
  border-radius: 8px;
  cursor: pointer;
  background-color: var(--color-surface-container-lowest);
  transition: all 0.2s ease;
}
.option-row:hover {
  border-color: var(--color-primary-container);
  background-color: var(--color-surface-container-low);
}
.option-row.selected {
  background-color: #eff6ff; /* Trust Blue Tint */
  border-color: var(--color-primary-container);
}
.dark-mode .option-row.selected {
  background-color: rgba(37, 99, 235, 0.15);
  border-color: var(--color-primary);
}

/* Custom radio indicator */
.radio-circle {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid var(--color-outline);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
  flex-shrink: 0;
}
.option-row.selected .radio-circle {
  border-color: var(--color-primary-container);
}
.radio-circle::after {
  content: "";
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background-color: var(--color-primary-container);
  transform: scale(0);
  transition: transform 0.2s ease;
}
.option-row.selected .radio-circle::after {
  transform: scale(1);
}

/* ===== SKELETON SHIMMER ===== */
.skeleton {
  background: linear-gradient(
    90deg,
    var(--color-outline-variant) 25%,
    var(--color-surface-container) 50%,
    var(--color-outline-variant) 75%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
}
@keyframes shimmer {
  0% {
    background-position: 200% 0;
  }
  100% {
    background-position: -200% 0;
  }
}

/* Page visibility for multi-page mode */
.section-visible {
  display: block;
}

#pdf-canvas {
  max-width: 100%;
  height: auto;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  border-radius: 4px;
}

/* Animations */
.pulse-num {
  animation: pulseOpacity 1.2s ease-in-out infinite;
}
@keyframes pulseOpacity {
  0%, 100% {
    opacity: 1;
    transform: scale(1);
  }
  50% {
    opacity: 0.8;
    transform: scale(1.02);
  }
}