/**
 * IELTS 7.5 Mastery - Duolingo 3D Design System & Responsive Shell
 * Mobile-first with Desktop responsive expansion (1024px+)
 */

:root {
  /* Duolingo Brand Palette */
  --duo-green: #58CC02;
  --duo-green-border: #46A302;
  --duo-green-hover: #61E002;
  --duo-green-light: #E5F6DF;

  --duo-blue: #1CB0F6;
  --duo-blue-border: #1899D6;
  --duo-blue-hover: #2CD2FF;
  --duo-blue-light: #DDF4FF;

  --duo-orange: #FF9600;
  --duo-orange-border: #E08500;
  --duo-orange-hover: #FFA51E;
  --duo-orange-light: #FFF0DB;

  --duo-red: #FF4B4B;
  --duo-red-border: #EA2B2B;
  --duo-red-hover: #FF6161;
  --duo-red-light: #FFEAEA;

  --duo-yellow: #FFC800;
  --duo-yellow-border: #E5A800;
  --duo-yellow-hover: #FFD21A;
  --duo-yellow-light: #FFF9DB;

  --duo-gray: #E5E5E5;
  --duo-gray-border: #CECECE;
  --duo-gray-hover: #F0F0F0;

  --duo-text-dark: #3C3C3C;
  --duo-text-muted: #777777;

  /* Shell Unified Color Schemes (Desktop Sidebar & Mobile Bottom Bar 100% synchronized) */
  --nav-bg-light: #FFFFFF;
  --nav-border-light: #E5E5E5;
  --nav-bg-dark: #1E2124;
  --nav-border-dark: #2D3238;

  --card-radius: 24px;
}

/* Base Body Setup */
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background-color: #F7F7F7;
  color: var(--duo-text-dark);
  -webkit-tap-highlight-color: transparent;
  margin: 0;
  padding: 0;
  min-height: 100vh;
}

body.dark-mode, .dark body {
  background-color: #121416;
  color: #F5F5F5;
}

/* ==========================================================================
   1. DUOLINGO 3D BUTTON PRESS SYSTEM
   ========================================================================== */

.duo-btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.875rem;
  border-radius: 16px;
  padding: 12px 20px;
  cursor: pointer;
  user-select: none;
  border: none;
  outline: none;
  text-decoration: none;
  transition: transform 0.08s ease, box-shadow 0.08s ease, filter 0.08s ease, background-color 0.15s ease;
  -webkit-tap-highlight-color: transparent;
}

/* Green (Primary Success / Next / Confirm) */
.duo-btn-green {
  background-color: var(--duo-green);
  color: #FFFFFF;
  border-bottom: 4px solid var(--duo-green-border);
  box-shadow: 0 4px 0 var(--duo-green-border);
}
.duo-btn-green:hover {
  background-color: var(--duo-green-hover);
}
.duo-btn-green:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-green-border);
  border-bottom-width: 2px;
}

/* Blue (Action / SRS Good / Input) */
.duo-btn-blue {
  background-color: var(--duo-blue);
  color: #FFFFFF;
  border-bottom: 4px solid var(--duo-blue-border);
  box-shadow: 0 4px 0 var(--duo-blue-border);
}
.duo-btn-blue:hover {
  background-color: var(--duo-blue-hover);
}
.duo-btn-blue:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-blue-border);
  border-bottom-width: 2px;
}

/* Orange (Caution / Hard / Streak) */
.duo-btn-orange {
  background-color: var(--duo-orange);
  color: #FFFFFF;
  border-bottom: 4px solid var(--duo-orange-border);
  box-shadow: 0 4px 0 var(--duo-orange-border);
}
.duo-btn-orange:hover {
  background-color: var(--duo-orange-hover);
}
.duo-btn-orange:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-orange-border);
  border-bottom-width: 2px;
}

/* Red (Danger / Again / Delete) */
.duo-btn-red {
  background-color: var(--duo-red);
  color: #FFFFFF;
  border-bottom: 4px solid var(--duo-red-border);
  box-shadow: 0 4px 0 var(--duo-red-border);
}
.duo-btn-red:hover {
  background-color: var(--duo-red-hover);
}
.duo-btn-red:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-red-border);
  border-bottom-width: 2px;
}

/* Yellow (Warning / Easy / Gold) */
.duo-btn-yellow {
  background-color: var(--duo-yellow);
  color: #4B4B4B;
  border-bottom: 4px solid var(--duo-yellow-border);
  box-shadow: 0 4px 0 var(--duo-yellow-border);
}
.duo-btn-yellow:hover {
  background-color: var(--duo-yellow-hover);
}
.duo-btn-yellow:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-yellow-border);
  border-bottom-width: 2px;
}

/* White / Outline (Secondary / Neutral) */
.duo-btn-white {
  background-color: #FFFFFF;
  color: var(--duo-text-dark);
  border: 2px solid var(--duo-gray);
  border-bottom: 4px solid var(--duo-gray-border);
  box-shadow: 0 4px 0 var(--duo-gray-border);
}
.duo-btn-white:hover {
  background-color: #F7F7F7;
}
.duo-btn-white:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-gray-border);
  border-bottom-width: 2px;
}

/* Gray / Disabled */
.duo-btn-gray {
  background-color: #E5E5E5;
  color: #A0A0A0;
  border-bottom: 4px solid var(--duo-gray-border);
  box-shadow: 0 4px 0 var(--duo-gray-border);
}
.duo-btn-gray:hover {
  background-color: #EDEDED;
}
.duo-btn-gray:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-gray-border);
  border-bottom-width: 2px;
}

/* Size modifiers */
.duo-btn-sm {
  padding: 8px 14px;
  font-size: 0.75rem;
  border-radius: 12px;
  border-bottom-width: 3px;
  box-shadow: 0 3px 0 rgba(0, 0, 0, 0.15);
}
.duo-btn-sm:active {
  transform: translateY(1px);
  box-shadow: 0 1px 0 rgba(0, 0, 0, 0.15);
}

.duo-btn-lg {
  padding: 14px 28px;
  font-size: 1rem;
  border-radius: 20px;
  border-bottom-width: 5px;
  box-shadow: 0 5px 0 rgba(0, 0, 0, 0.2);
}
.duo-btn-lg:active {
  transform: translateY(3px);
  box-shadow: 0 2px 0 rgba(0, 0, 0, 0.2);
}

.duo-btn-block {
  width: 100%;
}

/* ==========================================================================
   2. DUOLINGO 3D CARDS
   ========================================================================== */

.duo-card {
  background-color: #FFFFFF;
  border-radius: 24px;
  border: 2px solid #E5E5E5;
  box-shadow: 0 4px 0 #E5E5E5;
  padding: 20px;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
  position: relative;
}

.duo-card-clickable {
  cursor: pointer;
  user-select: none;
}
.duo-card-clickable:hover {
  border-color: var(--duo-blue);
  transform: translateY(-2px);
  box-shadow: 0 6px 0 var(--duo-gray);
}
.duo-card-clickable:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--duo-gray);
}

/* Dark Mode Cards */
body.dark-mode .duo-card,
.dark .duo-card {
  background-color: #1E2124;
  border-color: #2D3238;
  box-shadow: 0 4px 0 #2D3238;
  color: #F5F5F5;
}

/* ==========================================================================
   3. UNIFIED NAVIGATION SHELL (Mobile Bottom Bar & Desktop Sidebar)
   Exact match: #FFFFFF (light) / #1E2124 (dark), border #E5E5E5 / #2D3238
   ========================================================================== */

/* Mobile Bottom Navigation Bar (Fixed bottom, 375px-430px optimized) */
.nav-bottom-bar {
  display: flex;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: calc(64px + env(safe-area-inset-bottom, 0px));
  padding-bottom: env(safe-area-inset-bottom, 0px);
  background-color: #FFFFFF;
  border-top: 2px solid #E5E5E5;
  z-index: 50;
  justify-content: space-around;
  align-items: center;
  box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.04);
}

/* Desktop Sidebar (Left side, >= 1024px) */
.nav-sidebar {
  display: none;
}

/* Nav Item (Shared logic, responsive styling) */
.nav-item {
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  color: var(--duo-text-muted);
  cursor: pointer;
  user-select: none;
  transition: all 0.15s ease;
  -webkit-tap-highlight-color: transparent;
}

/* Mobile Nav Item specific styling */
.nav-bottom-bar .nav-item {
  flex: 1;
  flex-direction: column;
  height: 100%;
  padding: 4px 2px;
  border-radius: 12px;
  margin: 2px;
  background: transparent;
  border: none;
}

.nav-bottom-bar .nav-item .nav-label {
  font-size: 11px;
  font-weight: 700;
  margin-top: 2px;
  white-space: nowrap;
  letter-spacing: -0.2px;
}

.nav-bottom-bar .nav-item:hover {
  color: var(--duo-text-dark);
  background-color: rgba(0, 0, 0, 0.03);
}

.nav-bottom-bar .nav-item.active {
  color: var(--duo-green);
  font-weight: 800;
  background-color: #F7FBF4;
}

.nav-bottom-bar .nav-item.active .nav-label {
  color: var(--duo-green);
}

/* Responsive expansion for Desktop (min-width: 1024px) */
@media (min-width: 1024px) {
  /* Hide Mobile Bottom Bar on Desktop */
  .nav-bottom-bar {
    display: none !important;
  }

  /* Show Left Sidebar on Desktop */
  .nav-sidebar {
    display: flex !important;
    flex-direction: column;
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    width: 256px;
    background-color: #FFFFFF;
    border-right: 2px solid #E5E5E5;
    z-index: 50;
    padding: 24px 16px;
    box-shadow: 2px 0 10px rgba(0, 0, 0, 0.02);
    overflow-y: auto;
  }

  /* Desktop Nav Item styling */
  .nav-sidebar .nav-item {
    display: flex !important;
    flex-direction: row !important;
    align-items: center !important;
    justify-content: flex-start !important;
    gap: 14px;
    width: 100%;
    padding: 12px 16px;
    border-radius: 16px;
    border: 2px solid transparent;
    font-weight: 800;
    font-size: 14px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--duo-text-muted);
    margin-bottom: 6px;
    background: transparent;
    text-align: left;
  }

  .nav-sidebar .nav-item lottie-player {
    flex-shrink: 0;
  }

  .nav-sidebar .nav-item .nav-label {
    font-size: 13px;
    font-weight: 800;
    text-align: left;
    white-space: nowrap;
  }

  .nav-sidebar .nav-item:hover {
    color: var(--duo-text-dark);
    background-color: #F7F7F7;
    border-color: #E5E5E5;
  }

  .nav-sidebar .nav-item.active {
    color: var(--duo-blue);
    background-color: var(--duo-blue-light);
    border-color: #84D8FF;
  }

  .nav-sidebar .nav-item.active .nav-label {
    color: var(--duo-blue);
  }
}

/* Mobile Top Header */
.mobile-top-header {
  height: 56px;
  background-color: #FFFFFF;
  border-bottom: 2px solid #E5E5E5;
}

/* Dark mode theme consistency for Navigation & Header */
body.dark-mode .mobile-top-header,
body.dark-mode .nav-bottom-bar,
body.dark-mode .nav-sidebar,
.dark .mobile-top-header,
.dark .nav-bottom-bar,
.dark .nav-sidebar {
  background-color: #1E2124 !important;
  border-color: #2D3238 !important;
  color: #A0A0A0 !important;
}

body.dark-mode .nav-bottom-bar .nav-item.active,
.dark .nav-bottom-bar .nav-item.active {
  background-color: #262B30 !important;
  color: var(--duo-green) !important;
}

body.dark-mode .nav-sidebar .nav-item:hover,
.dark .nav-sidebar .nav-item:hover {
  background-color: #262B30 !important;
  border-color: #2D3238 !important;
  color: #FFFFFF !important;
}

body.dark-mode .nav-sidebar .nav-item.active,
.dark .nav-sidebar .nav-item.active {
  background-color: #1A3142 !important;
  border-color: #1899D6 !important;
  color: var(--duo-blue) !important;
}

/* ==========================================================================
   4. LAYOUT AND MAIN CONTAINER
   ========================================================================== */

.app-layout {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

@media (min-width: 1024px) {
  .app-layout {
    flex-direction: row;
  }
}

.app-main {
  flex: 1;
  width: 100%;
  min-height: 100vh;
  padding: 16px;
  /* Compensate for 56px fixed mobile top header + safe area */
  padding-top: calc(56px + 16px + env(safe-area-inset-top, 0px));
  /* Safe padding bottom for mobile bottom nav bar */
  padding-bottom: calc(76px + env(safe-area-inset-bottom, 0px));
  box-sizing: border-box;
}

@media (min-width: 1024px) {
  .app-main {
    margin-left: 256px;
    width: calc(100% - 256px);
    padding: 32px 48px;
    padding-top: 32px;
    padding-bottom: 40px;
  }
}

/* ==========================================================================
   5. GAMIFICATION UI: BADGES, PROGRESS, SPEECH BUBBLES
   ========================================================================== */

/* Gamification Stats Header */
.duo-stat-pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  min-height: 38px;
  box-sizing: border-box;
  font-weight: 800;
  font-size: 0.875rem;
  padding: 6px 12px;
  border-radius: 12px;
  background-color: #FFFFFF;
  border: 2px solid #E5E5E5;
  box-shadow: 0 2px 0 #E5E5E5;
}

.duo-stat-pill.fire {
  color: var(--duo-orange);
}
.duo-stat-pill.gem {
  color: var(--duo-blue);
}
.duo-stat-pill.heart {
  color: var(--duo-red);
}

/* Mascot Speech Bubble */
.duo-speech-bubble {
  position: relative;
  background: #FFFFFF;
  border: 2px solid #E5E5E5;
  border-radius: 18px;
  padding: 12px 18px;
  box-shadow: 0 3px 0 #E5E5E5;
  font-weight: 600;
  font-size: 0.9375rem;
  line-height: 1.4;
  color: var(--duo-text-dark);
}

.duo-speech-bubble::before {
  content: "";
  position: absolute;
  left: 50%;
  top: -8px;
  transform: translateX(-50%) rotate(135deg);
  width: 12px;
  height: 12px;
  background: #FFFFFF;
  border-left: 2px solid #E5E5E5;
  border-bottom: 2px solid #E5E5E5;
}

@media (min-width: 640px) {
  .duo-speech-bubble::before {
    left: -8px;
    top: 50%;
    transform: translateY(-50%) rotate(45deg);
  }
}

/* Duolingo Progress Bar */
.duo-progress {
  width: 100%;
  height: 14px;
  background-color: #E5E5E5;
  border-radius: 9999px;
  overflow: hidden;
  position: relative;
}

.duo-progress-fill {
  height: 100%;
  border-radius: 9999px;
  background-color: var(--duo-green);
  transition: width 0.4s ease;
  position: relative;
}

.duo-progress-fill::after {
  content: "";
  position: absolute;
  top: 2px;
  left: 6px;
  right: 6px;
  height: 4px;
  border-radius: 9999px;
  background: rgba(255, 255, 255, 0.35);
}

/* Lottie Player container helper */
lottie-player {
  display: inline-block;
  vertical-align: middle;
  pointer-events: none;
}

/* ==========================================================================
   6. INTERACTIVE READER & DUOLINGO BOTTOM SHEET / POPOVER
   ========================================================================== */

.readable-word {
  cursor: pointer;
  display: inline-block;
  padding: 1px 3px;
  margin: 1px 0;
  border-radius: 6px;
  transition: all 0.15s ease;
  user-select: text;
  -webkit-tap-highlight-color: transparent;
}

.readable-word:hover {
  background-color: var(--duo-green-light);
  color: var(--duo-green-border);
}

.readable-word:active {
  background-color: var(--duo-blue-light);
  transform: scale(0.96);
}

.readable-word.in-vault {
  background-color: var(--duo-yellow-light);
  border-bottom: 2px solid var(--duo-yellow-border);
  font-weight: 600;
  color: #7A5700;
}

.readable-word.in-vault:hover {
  background-color: #FFECA0;
}

/* Duolingo Bottom Sheet (Mobile) & Popover (Desktop) */
.duo-sheet-backdrop {
  position: fixed;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(4px);
  z-index: 100;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}

.duo-sheet-backdrop.active {
  opacity: 1;
  pointer-events: auto;
}

.duo-bottom-sheet {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 101;
  background-color: #FFFFFF;
  border-top-left-radius: 28px;
  border-top-right-radius: 28px;
  border-top: 3px solid var(--duo-gray);
  box-shadow: 0 -8px 24px rgba(0, 0, 0, 0.15);
  transform: translateY(105%);
  transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
  max-height: 85vh;
  display: flex;
  flex-direction: column;
  padding-bottom: env(safe-area-inset-bottom, 16px);
}

.duo-bottom-sheet.active {
  transform: translateY(0);
}

.duo-sheet-handle {
  width: 44px;
  height: 5px;
  background-color: var(--duo-gray-border);
  border-radius: 9999px;
  margin: 10px auto 4px;
  cursor: pointer;
}

/* Desktop Popover Modal transformation for screen >= 1024px */
@media (min-width: 1024px) {
  .duo-bottom-sheet {
    left: 50%;
    right: auto;
    bottom: auto;
    top: 50%;
    transform: translate(-50%, -45%) scale(0.95);
    border-radius: 24px;
    border: 3px solid var(--duo-gray);
    width: 540px;
    max-height: 88vh;
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.18);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.25s ease;
  }

  .duo-bottom-sheet.active {
    transform: translate(-50%, -50%) scale(1);
    opacity: 1;
    pointer-events: auto;
  }

  .duo-sheet-handle {
    display: none;
  }
}

/* Dark mode bottom sheet support */
body.dark-mode .duo-bottom-sheet,
.dark .duo-bottom-sheet {
  background-color: #1E2124;
  border-color: #2D3238;
  color: #F5F5F5;
}