/* ==========================================================================
   DESIGN SYSTEM & CUSTOM PROPERTIES
   ========================================================================== */

:root {
  /* Font Families */
  --font-heading: 'Outfit', sans-serif;
  --font-body: 'Inter', sans-serif;

  /* Common Transition */
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: all 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 8px 30px rgba(0, 0, 0, 0.12);
  --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.25);
  --radius-sm: 8px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-full: 9999px;
}

/* Dark Theme Variables (Default) */
.dark-theme {
  --primary: #8b5cf6;
  --primary-gradient: linear-gradient(135deg, #8b5cf6 0%, #3b82f6 100%);
  --primary-glow: rgba(139, 92, 246, 0.4);
  --secondary: #3b82f6;
  --secondary-gradient: linear-gradient(135deg, #3b82f6 0%, #06b6d4 100%);
  
  --bg-gradient: radial-gradient(circle at 10% 20%, #0f172a 0%, #090d16 100%);
  --bg-app: #090d16;
  --card-bg: rgba(30, 41, 59, 0.45);
  --card-hover-bg: rgba(30, 41, 59, 0.6);
  --border-color: rgba(255, 255, 255, 0.08);
  --border-hover-color: rgba(255, 255, 255, 0.18);
  
  --text-main: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --text-white: #ffffff;
  
  --success: #10b981;
  --success-glow: rgba(16, 185, 129, 0.3);
  --danger: #f43f5e;
  --danger-glow: rgba(244, 63, 94, 0.3);
  --warning: #f59e0b;
  
  --glass-reflection: linear-gradient(135deg, rgba(255, 255, 255, 0.05) 0%, rgba(255, 255, 255, 0) 100%);
  --input-bg: rgba(15, 23, 42, 0.6);
  --table-header-bg: rgba(15, 23, 42, 0.5);
  --row-alt-bg: rgba(255, 255, 255, 0.015);
}

/* Light Theme Variables */
.light-theme {
  --primary: #6366f1;
  --primary-gradient: linear-gradient(135deg, #6366f1 0%, #4f46e5 100%);
  --primary-glow: rgba(99, 102, 241, 0.25);
  --secondary: #0ea5e9;
  --secondary-gradient: linear-gradient(135deg, #0ea5e9 0%, #2563eb 100%);
  
  --bg-gradient: radial-gradient(circle at 10% 20%, #f8fafc 0%, #e2e8f0 100%);
  --bg-app: #f8fafc;
  --card-bg: rgba(255, 255, 255, 0.7);
  --card-hover-bg: rgba(255, 255, 255, 0.85);
  --border-color: rgba(15, 23, 42, 0.08);
  --border-hover-color: rgba(15, 23, 42, 0.16);
  
  --text-main: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --text-white: #ffffff;
  
  --success: #10b981;
  --success-glow: rgba(16, 185, 129, 0.2);
  --danger: #e11d48;
  --danger-glow: rgba(225, 29, 72, 0.2);
  --warning: #d97706;
  
  --glass-reflection: linear-gradient(135deg, rgba(255, 255, 255, 0.4) 0%, rgba(255, 255, 255, 0) 100%);
  --input-bg: rgba(255, 255, 255, 0.9);
  --table-header-bg: rgba(241, 245, 249, 0.9);
  --row-alt-bg: rgba(15, 23, 42, 0.015);
}

/* ==========================================================================
   RESET & BASE STYLES
   ========================================================================== */

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  outline: none;
}

body {
  font-family: var(--font-body);
  color: var(--text-main);
  background-color: var(--bg-app);
  background-image: var(--bg-gradient);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  overflow-x: hidden;
  transition: background-color 0.4s ease, color 0.4s ease;
}

canvas#particles-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 0;
  pointer-events: none;
}

/* ==========================================================================
   LAYOUT STRUCTURE
   ========================================================================== */

.app-container {
  width: 100%;
  max-width: 1200px;
  min-height: 100vh;
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  position: relative;
  z-index: 1;
}

.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 1.5rem;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-radius: var(--radius-md);
  margin-bottom: 2rem;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

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

.logo-icon {
  background: var(--primary-gradient);
  color: var(--text-white);
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 12px var(--primary-glow);
}

.logo-text h1 {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 700;
  line-height: 1.2;
}

.logo-text span {
  font-size: 0.75rem;
  color: var(--text-secondary);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

/* Streak Badge */
.streak-badge {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  background: rgba(245, 158, 11, 0.15);
  border: 1px solid rgba(245, 158, 11, 0.3);
  color: var(--warning);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-full);
  font-weight: 700;
  font-size: 0.875rem;
  font-family: var(--font-heading);
  transition: var(--transition);
}

.fire-icon {
  animation: flicker 1.5s infinite alternate;
}

@keyframes flicker {
  0% { transform: scale(0.95); filter: drop-shadow(0 0 2px rgba(245, 158, 11, 0.5)); }
  100% { transform: scale(1.05); filter: drop-shadow(0 0 8px rgba(245, 158, 11, 0.8)); }
}

/* Mastery Gauge */
.mastery-mini-gauge {
  position: relative;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  cursor: pointer;
}

.progress-ring {
  transform: rotate(-90deg);
}

.progress-ring__circle {
  transition: stroke-dashoffset 0.35s;
  transform-origin: 50% 50%;
  stroke-dasharray: 87.96; /* 2 * PI * r (r=14) */
  stroke-dashoffset: 87.96;
}

#header-progress-text {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.875rem;
}

/* Theme Toggle Button */
.icon-btn {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
}

.icon-btn:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: var(--border-hover-color);
  transform: scale(1.05);
}

.app-main {
  flex: 1;
  display: flex;
  flex-direction: column;
}

/* ==========================================================================
   APP SCREENS (SPA ARCHITECTURE)
   ========================================================================== */

.app-screen {
  display: none;
  width: 100%;
  opacity: 0;
  transform: translateY(15px);
  transition: opacity 0.4s ease, transform 0.4s ease;
}

.app-screen.active {
  display: block;
  opacity: 1;
  transform: translateY(0);
}

/* ==========================================================================
   SCREEN 1: DASHBOARD
   ========================================================================== */

.hero-card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 2rem;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-md);
  margin-bottom: 2rem;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.hero-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 150px;
  height: 100%;
  background: var(--glass-reflection);
  transform: skewX(-25deg) translateX(-150px);
  transition: var(--transition-slow);
  pointer-events: none;
}

.hero-card:hover::before {
  transform: skewX(-25deg) translateX(800px);
}

.hero-content {
  flex: 1;
}

.hero-content h2 {
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-content p {
  color: var(--text-secondary);
  font-size: 1rem;
  line-height: 1.6;
  max-width: 500px;
  margin-bottom: 1.5rem;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

/* Button UI */
.btn {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.95rem;
  padding: 0.6rem 1.25rem;
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  transition: var(--transition);
}

.large-btn {
  padding: 0.8rem 1.75rem;
  border-radius: var(--radius-md);
  font-size: 1.05rem;
}

.primary-btn {
  background: var(--primary-gradient);
  color: var(--text-white);
  box-shadow: 0 4px 14px var(--primary-glow);
}

.primary-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px var(--primary-glow);
}

.secondary-btn {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-main);
  border: 1px solid var(--border-color);
}

.secondary-btn:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: var(--border-hover-color);
  transform: translateY(-2px);
}

.success-btn {
  background: var(--success);
  color: var(--text-white);
  box-shadow: 0 4px 14px var(--success-glow);
}

.success-btn:hover {
  box-shadow: 0 8px 20px var(--success-glow);
}

.text-link-btn {
  background: none;
  border: none;
  color: var(--primary);
  font-weight: 700;
  font-family: var(--font-heading);
  cursor: pointer;
  transition: var(--transition);
}

.text-link-btn:hover {
  color: var(--secondary);
  text-decoration: underline;
}

.full-width {
  width: 100%;
}

/* Mastery Large Ring */
.hero-stats {
  display: flex;
  justify-content: center;
  align-items: center;
}

.stat-circle-container {
  position: relative;
  width: 130px;
  height: 130px;
  display: flex;
  justify-content: center;
  align-items: center;
}

.mastery-large-ring {
  transform: rotate(-90deg);
}

.ring-fg {
  stroke-dasharray: 314.16; /* 2 * PI * r (r=50) */
  stroke-dashoffset: 314.16;
  transition: stroke-dashoffset 0.8s cubic-bezier(0.4, 0, 0.2, 1);
  stroke-linecap: round;
}

.ring-text {
  position: absolute;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.ring-text span {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 800;
  line-height: 1.1;
}

.ring-text label {
  font-size: 0.68rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  font-weight: 600;
  letter-spacing: 0.5px;
}

/* STATS GRID */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.25rem;
  margin-bottom: 2rem;
}

.stat-card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: var(--transition);
}

.stat-card:hover {
  transform: translateY(-3px);
  border-color: var(--border-hover-color);
  box-shadow: var(--shadow-md);
}

.stat-icon {
  width: 46px;
  height: 46px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-white);
}

.purple-bg { background: linear-gradient(135deg, #a78bfa 0%, #7c3aed 100%); }
.orange-bg { background: linear-gradient(135deg, #fbbf24 0%, #d97706 100%); }
.blue-bg { background: linear-gradient(135deg, #60a5fa 0%, #2563eb 100%); }
.red-bg { background: linear-gradient(135deg, #f43f5e 0%, #be123c 100%); }
.green-bg { background: linear-gradient(135deg, #34d399 0%, #059669 100%); }

.stat-info h3 {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 800;
  line-height: 1.2;
}

.stat-info p {
  font-size: 0.78rem;
  color: var(--text-secondary);
  font-weight: 500;
}

/* DASHBOARD COLUMNS Layout */
.dashboard-sections {
  display: flex;
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.dashboard-column {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.flex-2 { flex: 2; }
.flex-1 { flex: 1.2; }

.section-title-wrapper {
  margin-bottom: 1.25rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 0.75rem;
}

.section-title-wrapper h3 {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 0.2rem;
}

.section-title-wrapper p {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* GROUPS GRID */
.groups-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
  gap: 1rem;
}

.group-selector-card {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
}

.group-selector-card:hover {
  background: rgba(255, 255, 255, 0.05);
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(139, 92, 246, 0.15);
}

.group-badge {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 800;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--primary-gradient);
  color: var(--text-white);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 0.5rem;
}

.group-name {
  font-size: 0.8rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.group-progress-bar {
  width: 100%;
  height: 5px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-bottom: 0.35rem;
}

.group-progress-fill {
  height: 100%;
  background: var(--success);
  width: 0%;
  transition: width 0.5s ease;
}

.group-progress-text {
  font-size: 0.7rem;
  color: var(--text-secondary);
  font-weight: 600;
}

/* WEAK VERBS / RECOMMENDATIONS */
.weak-verbs-card {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  max-height: 400px;
  overflow-y: auto;
  padding-right: 0.25rem;
}

.weak-verbs-card::-webkit-scrollbar {
  width: 5px;
}
.weak-verbs-card::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
}

.weak-verb-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.weak-verb-row:hover {
  background: rgba(255, 255, 255, 0.05);
  border-color: rgba(244, 63, 94, 0.3);
}

.wv-info {
  display: flex;
  flex-direction: column;
}

.wv-infinitive {
  font-weight: 700;
  font-size: 0.95rem;
}

.wv-translation {
  font-size: 0.78rem;
  color: var(--text-secondary);
}

.wv-stat {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
}

.wv-fails-badge {
  background: rgba(244, 63, 94, 0.15);
  border: 1px solid rgba(244, 63, 94, 0.3);
  color: var(--danger);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-full);
}

.wv-mastery-label {
  font-size: 0.65rem;
  color: var(--text-muted);
  margin-top: 0.15rem;
}

.no-verbs-message {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
  padding: 2rem 1rem;
}

/* ==========================================================================
   SCREEN 2: LIBRARY / STUDY LIST
   ========================================================================== */

.screen-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
}

.screen-title {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.back-btn {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
}

.back-btn:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: var(--border-hover-color);
  transform: translateX(-3px);
}

.screen-title h2 {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 800;
  line-height: 1.2;
}

.screen-title p {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

/* Search Bar */
.search-filter-bar {
  display: flex;
  gap: 1rem;
  margin-bottom: 1rem;
  flex-wrap: wrap;
}

.search-wrapper {
  flex: 1;
  min-width: 280px;
  position: relative;
  display: flex;
  align-items: center;
}

.search-icon {
  position: absolute;
  left: 0.95rem;
  color: var(--text-muted);
  pointer-events: none;
}

.search-wrapper input {
  width: 100%;
  padding: 0.8rem 1rem 0.8rem 2.6rem;
  background: var(--input-bg);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  transition: var(--transition);
}

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

.clear-btn {
  position: absolute;
  right: 1rem;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.5rem;
  cursor: pointer;
  line-height: 1;
}

.clear-btn:hover {
  color: var(--text-main);
}

.filter-dropdown-wrapper {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.filter-dropdown-wrapper label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
}

.filter-dropdown-wrapper select {
  padding: 0.8rem 1.5rem 0.8rem 1rem;
  background: var(--input-bg);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.filter-dropdown-wrapper select:focus {
  border-color: var(--primary);
}

/* Column Switches */
.memorize-controls {
  background: rgba(255, 255, 255, 0.015);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 0.85rem 1.25rem;
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.control-label {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-secondary);
}

.switch-grid {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.toggle-col-btn {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.4rem 0.85rem;
  border-radius: var(--radius-full);
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.toggle-col-btn.active {
  background: var(--primary-gradient);
  color: var(--text-white);
  border-color: transparent;
  box-shadow: 0 3px 8px var(--primary-glow);
}

.toggle-col-btn:hover:not(.active) {
  background: rgba(255, 255, 255, 0.1);
  border-color: var(--border-hover-color);
}

/* Verbs Table */
.verbs-list-wrapper {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.verbs-table-container {
  max-height: 550px;
  overflow-y: auto;
  width: 100%;
}

.verbs-table-container::-webkit-scrollbar {
  width: 8px;
}
.verbs-table-container::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
}

.verbs-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
}

.verbs-table th {
  background: var(--table-header-bg);
  padding: 1.1rem 1rem;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.88rem;
  text-transform: uppercase;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 10;
  letter-spacing: 0.5px;
}

.verbs-table td {
  padding: 1rem;
  border-bottom: 1px solid var(--border-color);
  font-size: 0.95rem;
  vertical-align: middle;
  transition: var(--transition);
}

.verbs-table tr:nth-child(even) {
  background-color: var(--row-alt-bg);
}

.verbs-table tr:hover {
  background-color: rgba(255, 255, 255, 0.03);
}

.center-align {
  text-align: center;
}

/* Phonetics & hidden items */
.word-cell {
  /* Se elimina display: flex para no romper el layout de tabla HTML nativo */
}

.word-cell strong {
  display: block;
  font-weight: 700;
  letter-spacing: 0.2px;
}

.phonetic {
  display: block;
  font-size: 0.72rem;
  color: var(--text-muted);
  font-family: var(--font-body);
  margin-top: 0.15rem;
}

/* Hidden cell interactive effect */
.cell-masked {
  background: rgba(139, 92, 246, 0.15) !important;
  border: 1px dashed var(--primary) !important;
  border-radius: var(--radius-sm);
  color: transparent !important;
  text-shadow: 0 0 10px var(--primary);
  user-select: none;
  cursor: pointer;
  transition: var(--transition);
}

.cell-masked .phonetic {
  visibility: hidden;
}

.cell-masked:hover {
  background: rgba(139, 92, 246, 0.25) !important;
  text-shadow: 0 0 4px var(--primary);
}

/* Master check box */
.mastery-checkbox-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.mastery-checkbox-btn:hover {
  color: var(--primary);
  transform: scale(1.15);
}

.mastery-checkbox-btn.mastered {
  color: var(--success);
}

.mastery-checkbox-btn.mastered svg {
  fill: var(--success);
}

/* Audio Play button */
.audio-circle-btn {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
}

.audio-circle-btn:hover {
  background: var(--primary-glow);
  color: var(--primary);
  border-color: var(--primary);
  transform: scale(1.1);
}

.mini-btn {
  width: 24px;
  height: 24px;
}

/* Table Group Header Divider */
.table-group-header {
  background: rgba(139, 92, 246, 0.05) !important;
}

.table-group-header td {
  padding: 0.5rem 1rem !important;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--primary);
  letter-spacing: 0.5px;
  border-bottom: 1px solid rgba(139, 92, 246, 0.15) !important;
}

/* ==========================================================================
   SCREEN 3: PRACTICE PAGE / CONFIG & ARENA
   ========================================================================== */

.practice-card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-md);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.practice-card-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 2rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 1rem;
}

.practice-card-header h2 {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 800;
}

.practice-card-header p {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

.config-sections {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.config-block {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.block-title {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.block-title h4 {
  font-family: var(--font-heading);
  font-size: 1.05rem;
  font-weight: 700;
}

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

/* Checkboxes grid for Groups */
.groups-checkbox-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
  gap: 0.75rem;
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  padding: 0.6rem 0.8rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  transition: var(--transition);
}

.checkbox-label:hover {
  background: rgba(255, 255, 255, 0.05);
  border-color: var(--border-hover-color);
}

.checkbox-label input[type="checkbox"] {
  accent-color: var(--primary);
  width: 16px;
  height: 16px;
  cursor: pointer;
}

/* Practice Mode selector cards */
.modes-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media(min-width: 768px) {
  .modes-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.mode-card-label {
  cursor: pointer;
  display: block;
}

.mode-card-label input[type="radio"] {
  display: none;
}

.mode-card-content {
  display: flex;
  gap: 1rem;
  padding: 1.1rem;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  transition: var(--transition);
  height: 100%;
}

.mode-card-content:hover {
  background: rgba(255, 255, 255, 0.04);
  border-color: var(--border-hover-color);
}

.mode-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-white);
  flex-shrink: 0;
}

.mode-meta {
  display: flex;
  flex-direction: column;
}

.mode-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.95rem;
  margin-bottom: 0.25rem;
}

.mode-desc {
  font-size: 0.78rem;
  color: var(--text-secondary);
  line-height: 1.4;
}

/* Active radio selection styles */
.mode-card-label input[type="radio"]:checked + .mode-card-content {
  border-color: var(--primary);
  background: rgba(139, 92, 246, 0.06);
  box-shadow: 0 4px 12px rgba(139, 92, 246, 0.15);
}

/* ==========================================================================
   PRACTICE PLAY ARENA
   ========================================================================== */

.arena-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 1.25rem;
  margin-bottom: 2rem;
}

.progress-bar-container {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.progress-bar-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-secondary);
}

.progress-bar-bg {
  width: 100%;
  height: 8px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: var(--primary-gradient);
  border-radius: var(--radius-full);
  transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.game-stage {
  padding: 0.5rem 0;
  min-height: 380px;
  display: flex;
  flex-direction: column;
}

.game-view {
  width: 100%;
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  animation: fadeIn 0.4s ease;
}

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

/* A. FLASHCARDS 3D CARD GRAPHICS */
.flashcard-3d-wrapper {
  perspective: 1000px;
  width: 100%;
  max-width: 440px;
  height: 280px;
  margin: 0 auto 2rem auto;
}

.flashcard-card {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
}

.flashcard-card.flipped {
  transform: rotateY(180deg);
}

.card-side {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  box-shadow: var(--shadow-lg);
}

.card-front {
  background: radial-gradient(circle at 50% 50%, rgba(139, 92, 246, 0.08) 0%, rgba(30, 41, 59, 0.5) 100%), var(--card-bg);
  z-index: 2;
}

.card-back {
  background: radial-gradient(circle at 50% 50%, rgba(59, 130, 246, 0.08) 0%, rgba(30, 41, 59, 0.5) 100%), var(--card-bg);
  transform: rotateY(180deg);
}

.card-hint {
  font-size: 0.8rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 700;
  letter-spacing: 0.5px;
  margin-bottom: 0.5rem;
}

.card-main-word {
  font-family: var(--font-heading);
  font-size: 2.25rem;
  font-weight: 800;
  text-align: center;
  margin-bottom: 1rem;
}

.card-group-tag {
  background: var(--primary-glow);
  color: var(--primary);
  border: 1px solid rgba(139, 92, 246, 0.2);
  padding: 0.25rem 0.75rem;
  font-size: 0.75rem;
  font-weight: 700;
  border-radius: var(--radius-full);
  margin-bottom: 0.5rem;
}

.card-click-tip {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-style: italic;
  margin-top: auto;
}

/* Flashcard Back design */
.fc-back-header {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.fc-forms-container {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  width: 100%;
}

.fc-form-row {
  display: flex;
  align-items: center;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-sm);
}

.fc-form-row label {
  font-size: 0.7rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 700;
  width: 80px;
}

.fc-form-row strong {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--text-main);
  flex: 1;
}

.fc-form-row .phonetic {
  font-size: 0.75rem;
}

.flashcard-controls {
  display: flex;
  justify-content: center;
  gap: 1rem;
  max-width: 440px;
  margin: 0 auto;
  width: 100%;
}

/* B. WRITING CHALLENGE GRAPHICS */
.question-prompt-card {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  margin-bottom: 1.5rem;
}

.prompt-main {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.prompt-translation {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 800;
}

.prompt-infinitive-hint {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.prompt-infinitive-hint strong {
  color: var(--primary);
  font-size: 1.05rem;
}

/* Inputs form design */
.writing-inputs-container {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  max-width: 460px;
  margin: 0 auto;
  width: 100%;
}

.writing-input-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.input-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.input-header label {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-secondary);
}

.input-field-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.input-field-wrapper input {
  width: 100%;
  padding: 0.8rem 1rem;
  background: var(--input-bg);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 700;
  transition: var(--transition);
}

.input-field-wrapper input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

/* Success/Error input decoration inside inputs */
.input-feedback-icon {
  position: absolute;
  right: 1rem;
  pointer-events: none;
}

.input-field-wrapper.correct input {
  border-color: var(--success);
  background: rgba(16, 185, 129, 0.05);
}

.input-field-wrapper.incorrect input {
  border-color: var(--danger);
  background: rgba(244, 63, 94, 0.05);
}

/* Spelling highlights */
.spelling-correction {
  font-size: 0.8rem;
  line-height: 1.4;
  padding: 0.25rem 0.5rem;
  border-radius: var(--radius-sm);
  display: none;
}

.spelling-correction.visible {
  display: block;
}

.spelling-incorrect {
  background: rgba(244, 63, 94, 0.1);
  color: var(--text-secondary);
  border: 1px solid rgba(244, 63, 94, 0.2);
}

.spelling-incorrect span.correct-char {
  color: var(--success);
  font-weight: 700;
}

.spelling-incorrect span.wrong-char {
  color: var(--danger);
  font-weight: 700;
  text-decoration: line-through;
}

.spelling-correct-reveal {
  color: var(--success);
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.writing-actions {
  display: flex;
  gap: 1rem;
  margin-top: 1rem;
}

.writing-actions button {
  flex: 1;
}

/* C. QUIZ MULTIPLE CHOICE OPTIONS */
.quiz-prompt-card {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  text-align: center;
  margin-bottom: 1.5rem;
}

.quiz-question-type-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  text-transform: uppercase;
  font-weight: 700;
  letter-spacing: 0.5px;
}

.quiz-question-word {
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 800;
  margin: 0.25rem 0;
}

.quiz-question-subtext {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.quiz-options-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
  max-width: 500px;
  margin: 0 auto;
  width: 100%;
}

@media(min-width: 560px) {
  .quiz-options-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.quiz-opt-btn {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 1rem;
  border-radius: var(--radius-md);
  font-family: var(--font-body);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  text-align: left;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.quiz-opt-btn:hover:not(:disabled) {
  background: rgba(255, 255, 255, 0.05);
  border-color: var(--border-hover-color);
  transform: translateY(-2px);
}

.opt-index {
  width: 24px;
  height: 24px;
  border-radius: var(--radius-full);
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-secondary);
}

/* Quiz Option States */
.quiz-opt-btn.correct {
  background: rgba(16, 185, 129, 0.1) !important;
  border-color: var(--success) !important;
  color: var(--success) !important;
}

.quiz-opt-btn.correct .opt-index {
  background: var(--success);
  border-color: transparent;
  color: var(--text-white);
}

.quiz-opt-btn.incorrect {
  background: rgba(244, 63, 94, 0.1) !important;
  border-color: var(--danger) !important;
  color: var(--danger) !important;
}

.quiz-opt-btn.incorrect .opt-index {
  background: var(--danger);
  border-color: transparent;
  color: var(--text-white);
}

/* D. COMPLETE TABLE STYLES */
.fill-table-card strong {
  color: var(--success);
  font-size: 1.3rem;
}

.interactive-table-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 1.25rem;
  max-width: 550px;
  margin: 0 auto;
  width: 100%;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.table-cell {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.table-cell label {
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 700;
  letter-spacing: 0.5px;
}

.table-cell-content {
  font-size: 1.1rem;
  font-weight: 700;
  min-height: 42px;
  display: flex;
  align-items: center;
}

.table-cell-content input {
  width: 100%;
  padding: 0.5rem 0.75rem;
  background: var(--input-bg);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 700;
  transition: var(--transition);
}

.table-cell-content input:focus {
  border-color: var(--primary);
}

/* ==========================================================================
   SCREEN 4: RESULTS SCREEN
   ========================================================================== */

.results-card {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  box-shadow: var(--shadow-lg);
  text-align: center;
  max-width: 600px;
  margin: 0 auto;
  width: 100%;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.results-celebration {
  margin-bottom: 1.75rem;
}

.results-medal-icon {
  font-size: 3.5rem;
  margin-bottom: 1rem;
  animation: bounce 1s infinite alternate;
}

@keyframes bounce {
  0% { transform: translateY(0); }
  100% { transform: translateY(-8px); }
}

.results-celebration h2 {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 800;
  margin-bottom: 0.25rem;
}

.results-celebration p {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.results-stats-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-bottom: 2rem;
}

.results-stat-box {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem 0.5rem;
}

.results-stat-box .stat-number {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 800;
  display: block;
  line-height: 1.1;
  margin-bottom: 0.25rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.results-stat-box .stat-label {
  font-size: 0.75rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.results-details-wrapper {
  text-align: left;
  margin-bottom: 2.25rem;
}

.results-details-wrapper h3 {
  font-family: var(--font-heading);
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
}

.results-verbs-checklist {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  max-height: 250px;
  overflow-y: auto;
  padding-right: 0.25rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 0.75rem;
  background: rgba(15, 23, 42, 0.15);
}

.results-verbs-checklist::-webkit-scrollbar {
  width: 5px;
}
.results-verbs-checklist::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
}

.checklist-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.03);
  font-size: 0.88rem;
}

.checklist-row:last-child {
  border-bottom: none;
}

.checklist-left {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
}

.checklist-verb-forms {
  color: var(--text-secondary);
  font-size: 0.78rem;
  font-weight: 400;
}

.icon-correct {
  color: var(--success);
}

.icon-incorrect {
  color: var(--danger);
}

.checklist-translation {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.results-actions {
  display: flex;
  gap: 1rem;
}

.results-actions button {
  flex: 1;
}

/* ==========================================================================
   APP FOOTER
   ========================================================================== */

.app-footer {
  text-align: center;
  padding: 1.5rem 0;
  color: var(--text-muted);
  font-size: 0.75rem;
  margin-top: auto;
  border-top: 1px solid var(--border-color);
}

/* ==========================================================================
   MEDIA QUERIES FOR COMPACT SCREEN SIZES
   ========================================================================== */

@media(max-width: 900px) {
  .dashboard-sections {
    flex-direction: column;
  }
  .hero-card {
    flex-direction: column;
    text-align: center;
    padding: 1.5rem;
  }
  .hero-content {
    display: flex;
    flex-direction: column;
    align-items: center;
  }
  .hero-actions {
    justify-content: center;
  }
}

@media(max-width: 600px) {
  .app-container {
    padding: 0.75rem;
  }
  .app-header {
    padding: 0.75rem;
    flex-direction: column;
    gap: 1rem;
    align-items: stretch;
  }
  .logo-area {
    justify-content: center;
  }
  .header-actions {
    justify-content: center;
  }
  .hero-content h2 {
    font-size: 1.5rem;
  }
  .results-stats-row {
    grid-template-columns: 1fr;
  }
  .results-actions {
    flex-direction: column;
  }
  .memorize-controls {
    flex-direction: column;
    align-items: stretch;
  }
  .switch-grid {
    justify-content: center;
  }
}