/* ==========================================================================
   Catchup - Adaptive Study Planner Stylesheet (Polished Edition)
   Modern, cohesive, mobile-first design with dark/light mode, micro-interactions,
   accessible dialogs, and prefers-reduced-motion support.
   ========================================================================== */

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

/* --- Theme Variables --- */
:root {
  --font-sans: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-display: 'Outfit', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Color Palette - Default Dark */
  --bg-primary: #0a0e17;
  --bg-secondary: #111827;
  --bg-surface: #172033;
  --bg-surface-hover: #1e293b;
  --bg-glass: rgba(17, 24, 39, 0.75);

  --border-subtle: #23314d;
  --border-strong: #334466;

  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  --primary: #6366f1;
  --primary-glow: rgba(99, 102, 241, 0.25);
  --primary-light: #818cf8;
  --primary-dark: #4f46e5;

  --accent-cyan: #06b6d4;
  --accent-emerald: #10b981;
  --accent-amber: #f59e0b;
  --accent-rose: #f43f5e;

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-full: 9999px;

  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 6px 16px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.35);

  --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-spring: 0.35s cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* Light Theme Override */
html[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-surface: #f1f5f9;
  --bg-surface-hover: #e2e8f0;
  --bg-glass: rgba(255, 255, 255, 0.85);

  --border-subtle: #e2e8f0;
  --border-strong: #cbd5e1;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;

  --primary: #4f46e5;
  --primary-glow: rgba(79, 70, 229, 0.15);
  --primary-light: #6366f1;
  --primary-dark: #3730a3;

  --shadow-sm: 0 2px 6px rgba(15, 23, 42, 0.05);
  --shadow-md: 0 8px 20px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 16px 36px rgba(15, 23, 42, 0.12);
}

/* Base Reset & Typography */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.5;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  display: flex;
  flex-direction: column;
}

h1, h2, h3, h4, .font-display {
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

button, input, select, textarea {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

a {
  color: var(--primary-light);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

/* Accessibility Focus States */
:focus-visible {
  outline: 2px solid var(--primary-light);
  outline-offset: 2px;
}

/* App Shell Container */
.app-container {
  max-width: 1180px;
  margin: 0 auto;
  width: 100%;
  padding: 1rem 1.25rem 3rem;
  flex: 1;
  display: flex;
  flex-direction: column;
}

/* Header & Navigation */
.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 0 1.5rem;
  border-bottom: 1px solid var(--border-subtle);
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
}

.brand-icon {
  width: 42px;
  height: 42px;
  background: linear-gradient(135deg, var(--primary), var(--accent-cyan));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 14px var(--primary-glow);
  color: white;
  font-weight: 800;
  font-size: 1.3rem;
  flex-shrink: 0;
}

.brand-title {
  font-size: 1.6rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--text-primary) 30%, var(--primary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.brand-badge {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.15rem 0.5rem;
  background: rgba(99, 102, 241, 0.15);
  border: 1px solid rgba(99, 102, 241, 0.3);
  color: var(--primary-light);
  border-radius: var(--radius-full);
  margin-left: 0.25rem;
}

.nav-controls {
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

/* Tab Navigation */
.tab-nav {
  display: flex;
  background: var(--bg-secondary);
  padding: 0.35rem;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-subtle);
  gap: 0.25rem;
  overflow-x: auto;
  max-width: 100%;
}

.tab-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1.1rem;
  min-height: 44px; /* Accessible touch target */
  border-radius: var(--radius-md);
  border: none;
  background: transparent;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 0.92rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.tab-btn:hover {
  color: var(--text-primary);
  background: var(--bg-surface-hover);
}

.tab-btn.active {
  background: var(--primary);
  color: white;
  box-shadow: 0 2px 10px var(--primary-glow);
}

.tab-btn svg {
  width: 18px;
  height: 18px;
}

/* Icon Buttons & Tooling */
.btn-icon {
  width: 44px; /* Accessible touch target */
  height: 44px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-subtle);
  background: var(--bg-secondary);
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-icon:hover {
  color: var(--text-primary);
  background: var(--bg-surface);
  border-color: var(--border-strong);
}

/* Standard Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  min-height: 44px; /* Accessible touch target */
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.92rem;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all var(--transition-fast);
  user-select: none;
}

.btn-primary {
  background: var(--primary);
  color: #ffffff;
  box-shadow: 0 4px 12px var(--primary-glow);
}
.btn-primary:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}
.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background: var(--bg-surface);
  color: var(--text-primary);
  border-color: var(--border-subtle);
}
.btn-secondary:hover {
  background: var(--bg-surface-hover);
  border-color: var(--border-strong);
}

.btn-warning {
  background: rgba(245, 158, 11, 0.15);
  color: #fbbf24;
  border: 1px solid rgba(245, 158, 11, 0.35);
}
.btn-warning:hover {
  background: rgba(245, 158, 11, 0.25);
  border-color: rgba(245, 158, 11, 0.5);
}

.btn-danger {
  background: rgba(244, 63, 94, 0.12);
  color: #fb7185;
  border: 1px solid rgba(244, 63, 94, 0.3);
}
.btn-danger:hover {
  background: rgba(244, 63, 94, 0.22);
}

.btn-sm {
  padding: 0.4rem 0.85rem;
  min-height: 36px;
  font-size: 0.85rem;
  border-radius: var(--radius-sm);
}

/* Workload Warning Banner */
.warning-banner {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.15), rgba(244, 63, 94, 0.15));
  border: 1px solid rgba(245, 158, 11, 0.4);
  border-radius: var(--radius-md);
  padding: 0.9rem 1.25rem;
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  animation: slideDown 0.3s ease;
}

.warning-content {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.warning-icon {
  color: #fbbf24;
  font-size: 1.4rem;
  flex-shrink: 0;
}

.warning-text h4 {
  font-size: 0.98rem;
  color: #fde68a;
  margin-bottom: 0.15rem;
}

.warning-text p {
  font-size: 0.88rem;
  color: var(--text-primary);
}

/* Tab Panels */
.tab-content {
  display: none;
  animation: fadeIn 0.2s ease-in-out;
}

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

/* Screen Headers */
.screen-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.screen-title {
  font-size: 1.65rem;
  font-weight: 800;
}

.screen-subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-top: 0.25rem;
}

/* Inline Form Validation */
.input-invalid {
  border-color: var(--accent-rose) !important;
  box-shadow: 0 0 0 1px var(--accent-rose) !important;
}

.form-error-msg {
  color: #fb7185;
  font-size: 0.8rem;
  font-weight: 600;
  margin-top: 0.35rem;
  display: none;
}

/* ==========================================================================
   SCREEN 1: SETUP
   ========================================================================== */
.setup-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}
@media (min-width: 860px) {
  .setup-grid {
    grid-template-columns: 350px 1fr;
  }
}

.setup-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.setup-card h3 {
  font-size: 1.2rem;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.form-group {
  margin-bottom: 1.25rem;
}

.form-label {
  display: block;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 0.4rem;
}

.form-control {
  width: 100%;
  padding: 0.7rem 0.9rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-control:focus {
  border-color: var(--primary-light);
  box-shadow: 0 0 0 1px var(--primary-light);
  outline: none;
}

.days-selector {
  display: flex;
  gap: 0.35rem;
  flex-wrap: wrap;
}

.day-checkbox-label {
  flex: 1;
  min-width: 38px;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  font-size: 0.85rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
}

.day-checkbox-label.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary-dark);
  box-shadow: 0 2px 8px var(--primary-glow);
}

/* Subject List Cards */
.subjects-container {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.subject-item-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.subject-item-card:hover {
  border-color: var(--border-strong);
  box-shadow: var(--shadow-md);
}

.subject-header-row {
  padding: 1.1rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border-subtle);
  background: rgba(255, 255, 255, 0.02);
  gap: 1rem;
}

.subject-title-area {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.color-dot {
  width: 14px;
  height: 14px;
  border-radius: var(--radius-full);
  flex-shrink: 0;
}

.subject-exam-badge {
  font-size: 0.82rem;
  font-weight: 600;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
  background: var(--bg-surface);
  color: var(--text-secondary);
}

.subject-exam-badge.urgent {
  background: rgba(244, 63, 94, 0.15);
  color: #fb7185;
  border: 1px solid rgba(244, 63, 94, 0.35);
}

.topics-table-area {
  padding: 1.1rem 1.25rem;
}

.topics-list {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.topic-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.7rem 0.9rem;
  background: var(--bg-surface);
  border-radius: var(--radius-md);
  font-size: 0.92rem;
  gap: 0.75rem;
}

.topic-info {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  flex: 1;
}

.difficulty-pill {
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.08);
  font-family: var(--font-mono);
}

.topic-hours-tag {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-family: var(--font-mono);
}

/* ==========================================================================
   SCREEN 2: TODAY (Hero Card, Daily Progress, Checklist & Pomodoro)
   ========================================================================== */
.today-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}
@media (min-width: 920px) {
  .today-layout {
    grid-template-columns: 1fr 370px;
  }
}

/* Today Hero Card */
.today-hero-card {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.12), rgba(6, 182, 212, 0.08));
  border: 1px solid var(--border-strong);
  border-left: 6px solid var(--hero-color, var(--primary));
  border-radius: var(--radius-lg);
  padding: 1.35rem 1.5rem;
  margin-bottom: 1.25rem;
  box-shadow: var(--shadow-sm);
  position: relative;
  overflow: hidden;
}

.today-hero-card.hero-completed {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.12), rgba(6, 182, 212, 0.08));
  border-left-color: var(--accent-emerald);
}

.hero-top-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 0.5rem;
}

.hero-pill {
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
}

.hero-title {
  font-size: 1.3rem;
  font-weight: 800;
  margin-bottom: 0.25rem;
}

.hero-sub {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.hero-actions {
  display: flex;
  gap: 0.75rem;
}

/* Daily Progress Bar Widget */
.today-progress-widget {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.85rem 1.25rem;
  margin-bottom: 1.25rem;
}

.daily-progress-header {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 0.45rem;
}

.daily-progress-track {
  width: 100%;
  height: 8px;
  background: var(--bg-surface);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.daily-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--accent-emerald));
  border-radius: var(--radius-full);
  transition: width 0.5s ease;
}

/* Quick Catchup Actions Bar */
.today-actions-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
  background: var(--bg-secondary);
  padding: 0.85rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-subtle);
}

.today-sessions-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.session-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.25rem;
  display: flex;
  align-items: center;
  gap: 1.25rem;
  position: relative;
  transition: all var(--transition-normal);
  box-shadow: var(--shadow-sm);
}

.session-card::before {
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 6px;
  border-top-left-radius: var(--radius-lg);
  border-bottom-left-radius: var(--radius-lg);
  background-color: var(--session-color, var(--primary));
}

.session-card.completed {
  opacity: 0.65;
  background: var(--bg-surface);
}

.session-card.completed .session-topic-title {
  text-decoration: line-through;
  color: var(--text-muted);
}

.session-checkbox-wrapper {
  display: flex;
  align-items: center;
  justify-content: center;
}

.custom-checkbox {
  width: 32px;
  height: 32px;
  border-radius: 9px;
  border: 2px solid var(--border-strong);
  background: var(--bg-surface);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
  padding: 0;
}

.custom-checkbox .check-svg {
  width: 18px;
  height: 18px;
  color: transparent;
  transition: all var(--transition-fast);
}

.custom-checkbox.checked {
  background: var(--accent-emerald);
  border-color: var(--accent-emerald);
  box-shadow: 0 0 10px rgba(16, 185, 129, 0.4);
}

.custom-checkbox.checked .check-svg {
  color: white;
  transform: scale(1.1);
}

.session-main-details {
  flex: 1;
}

.session-subject-tag {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
  display: inline-block;
  color: var(--session-color, var(--primary));
}

.session-topic-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.session-meta-tags {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.badge-revision {
  background: rgba(245, 158, 11, 0.15);
  color: #fbbf24;
  border: 1px solid rgba(245, 158, 11, 0.3);
  font-size: 0.75rem;
  padding: 0.1rem 0.5rem;
  border-radius: var(--radius-full);
  font-weight: 700;
}

/* Pomodoro Timer Widget */
.pomodoro-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.75rem 1.5rem;
  text-align: center;
  box-shadow: var(--shadow-md);
  position: sticky;
  top: 1.5rem;
}

.pomodoro-modes {
  display: flex;
  justify-content: center;
  background: var(--bg-surface);
  border-radius: var(--radius-full);
  padding: 0.25rem;
  margin-bottom: 1.5rem;
  gap: 0.25rem;
}

.pomo-mode-btn {
  flex: 1;
  border: none;
  background: transparent;
  padding: 0.5rem 0.8rem;
  min-height: 40px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.pomo-mode-btn.active {
  background: var(--primary);
  color: white;
  box-shadow: 0 2px 8px var(--primary-glow);
}

.timer-circle-wrap {
  position: relative;
  width: 210px;
  height: 210px;
  margin: 0 auto 1.5rem;
}

.timer-svg {
  transform: rotate(-90deg);
  width: 100%;
  height: 100%;
}

.timer-svg-bg {
  stroke: var(--bg-surface-hover);
  fill: none;
  stroke-width: 8px;
}

.timer-svg-progress {
  stroke: var(--primary-light);
  fill: none;
  stroke-width: 8px;
  stroke-linecap: round;
  transition: stroke-dashoffset 0.25s linear, stroke 0.3s ease;
}

.timer-svg-progress.break {
  stroke: var(--accent-emerald);
}

.timer-center-content {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.timer-time-display {
  font-family: var(--font-mono);
  font-size: 2.85rem;
  font-weight: 700;
  letter-spacing: -0.04em;
  color: var(--text-primary);
}

.timer-label-display {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-secondary);
  font-weight: 600;
}

.timer-controls-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
}

/* ==========================================================================
   SCREEN 3: PLAN (Calendar & Replan Animation)
   ========================================================================== */
.plan-calendar-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.25rem;
}
@media (min-width: 640px) {
  .plan-calendar-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (min-width: 1024px) {
  .plan-calendar-grid {
    grid-template-columns: repeat(7, 1fr);
  }
}

.calendar-day-col {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.85rem;
  display: flex;
  flex-direction: column;
  min-height: 220px;
  transition: all var(--transition-fast);
}

.calendar-day-col.today {
  border-color: var(--primary-light);
  box-shadow: 0 0 0 1px var(--primary-light), 0 4px 16px var(--primary-glow);
  background: linear-gradient(180deg, rgba(99, 102, 241, 0.08) 0%, var(--bg-secondary) 100%);
}

.calendar-day-col.non-study {
  opacity: 0.55;
  background: var(--bg-surface);
}

.calendar-day-header {
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 0.5rem;
  margin-bottom: 0.75rem;
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}

.day-name {
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.today-marker {
  font-size: 0.65rem;
  font-weight: 800;
  background: var(--primary);
  color: white;
  padding: 0.1rem 0.4rem;
  border-radius: var(--radius-full);
}

.day-date-number {
  font-size: 1rem;
  font-weight: 800;
  font-family: var(--font-display);
}

.day-sessions-stack {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  flex: 1;
}

.plan-session-pill {
  padding: 0.55rem 0.65rem;
  border-radius: var(--radius-sm);
  background: var(--bg-surface);
  border-left: 4px solid var(--session-color, var(--primary));
  font-size: 0.8rem;
  transition: all var(--transition-fast);
  cursor: pointer;
  position: relative;
}

.plan-session-pill:hover {
  background: var(--bg-surface-hover);
  transform: translateY(-1px);
}

.plan-session-pill.status-done {
  opacity: 0.6;
  text-decoration: line-through;
}

.plan-session-pill.status-missed {
  border-left-color: var(--accent-rose);
  background: rgba(244, 63, 94, 0.1);
}

.plan-session-pill.status-revision {
  border-left-color: var(--accent-amber);
  background: rgba(245, 158, 11, 0.12);
}

/* Dynamic Shift Highlight Animation on Re-plan */
@keyframes highlightShift {
  0% {
    transform: scale(0.92);
    box-shadow: 0 0 0 2px var(--primary);
  }
  50% {
    transform: scale(1.04);
    box-shadow: 0 0 16px var(--primary-glow);
  }
  100% {
    transform: scale(1);
    box-shadow: none;
  }
}

.replan-shifted {
  animation: highlightShift 0.7s cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* ==========================================================================
   SCREEN 4: PROGRESS (Readiness, Exam Countdowns & Heatmap)
   ========================================================================== */
.progress-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}
@media (min-width: 860px) {
  .progress-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.progress-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
}

.readiness-item {
  margin-bottom: 1.25rem;
}
.readiness-item:last-child {
  margin-bottom: 0;
}

.readiness-header-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.4rem;
  font-size: 0.92rem;
  font-weight: 600;
}

.progress-track {
  width: 100%;
  height: 10px;
  background: var(--bg-surface);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  border-radius: var(--radius-full);
  transition: width 0.6s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Exam Countdowns */
.countdown-cards-list {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.countdown-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.9rem 1.1rem;
  background: var(--bg-surface);
  border-radius: var(--radius-md);
  border-left: 4px solid var(--sub-color, var(--primary));
}

.days-left-badge {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.25rem;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-sm);
  background: var(--bg-surface-hover);
}

.days-left-badge.danger {
  color: #fb7185;
  background: rgba(244, 63, 94, 0.15);
}

.days-left-badge.warning {
  color: #fbbf24;
  background: rgba(245, 158, 11, 0.15);
}

/* GitHub-Style Study Activity Heatmap */
.heatmap-container-card {
  grid-column: 1 / -1;
  background: var(--bg-secondary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
}

.heatmap-scroll-wrapper {
  overflow-x: auto;
  padding-bottom: 0.5rem;
}

.heatmap-grid {
  display: grid;
  grid-template-rows: repeat(7, 16px);
  grid-auto-flow: column;
  grid-auto-columns: 16px;
  gap: 4px;
  width: max-content;
}

.heatmap-cell {
  width: 16px;
  height: 16px;
  border-radius: 3px;
  background: var(--bg-surface);
  cursor: pointer;
  transition: transform var(--transition-fast);
  position: relative;
}

.heatmap-cell:hover {
  transform: scale(1.3);
  z-index: 10;
}

.heatmap-cell[data-level="0"] { background: var(--bg-surface); }
.heatmap-cell[data-level="1"] { background: rgba(16, 185, 129, 0.3); }
.heatmap-cell[data-level="2"] { background: rgba(16, 185, 129, 0.55); }
.heatmap-cell[data-level="3"] { background: rgba(16, 185, 129, 0.8); }
.heatmap-cell[data-level="4"] { background: #10b981; box-shadow: 0 0 6px rgba(16, 185, 129, 0.5); }

.heatmap-legend {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 0.45rem;
  margin-top: 1rem;
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.legend-square {
  width: 12px;
  height: 12px;
  border-radius: 2px;
}

/* Modals */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 1rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease;
}

.modal-overlay.open {
  opacity: 1;
  pointer-events: auto;
}

.modal-dialog {
  background: var(--bg-secondary);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  max-width: 520px;
  width: 100%;
  padding: 1.75rem;
  box-shadow: var(--shadow-lg);
  transform: translateY(16px);
  transition: transform 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.modal-overlay.open .modal-dialog {
  transform: translateY(0);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.25rem;
}

.modal-footer {
  display: flex;
  justify-content: flex-end;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

/* Toast Notifications */
.toast-container {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  max-width: 390px;
  pointer-events: none;
}

.toast {
  pointer-events: auto;
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  padding: 0.95rem 1.15rem;
  color: var(--text-primary);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  font-size: 0.92rem;
  animation: slideInRight 0.3s cubic-bezier(0.16, 1, 0.3, 1);
  transition: opacity 0.25s ease, transform 0.25s ease;
}

.toast.toast-success {
  border-left: 4px solid var(--accent-emerald);
}

.toast.toast-info {
  border-left: 4px solid var(--primary-light);
}

.toast.toast-warning {
  border-left: 4px solid var(--accent-amber);
}

.toast.toast-danger {
  border-left: 4px solid var(--accent-rose);
}

.toast-icon {
  font-size: 1.15rem;
}

.toast-message {
  flex: 1;
}

.toast-close-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.2rem;
  font-size: 0.9rem;
}
.toast-close-btn:hover {
  color: var(--text-primary);
}

/* Empty States */
.empty-state {
  text-align: center;
  padding: 3rem 1.5rem;
  color: var(--text-secondary);
}

.empty-state-icon {
  font-size: 2.75rem;
  margin-bottom: 1rem;
}

.empty-state h3 {
  font-size: 1.3rem;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.empty-state p {
  max-width: 440px;
  margin: 0 auto 1.5rem;
  font-size: 0.95rem;
  line-height: 1.5;
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideInRight {
  from { opacity: 0; transform: translateX(20px); }
  to { opacity: 1; transform: translateX(0); }
}

/* Accessibility: Respect Reduced Motion Preferences */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Footer */
.app-footer {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-subtle);
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--text-muted);
  font-size: 0.85rem;
  flex-wrap: wrap;
  gap: 0.75rem;
}