* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --primary: #6c5ce7;
  --primary-dark: #5a4bd1;
  --secondary: #00cec9;
  --secondary-dark: #00b5b1;
  --accent: #fdcb6e;
  --success: #00b894;
  --error: #e17055;
  --warning: #fdcb6e;
  --bg-dark: #0a0a1a;
  --bg-card: #16162a;
  --bg-card-hover: #1e1e3a;
  --text-primary: #ffffff;
  --text-secondary: #b0b0cc;
  --text-muted: #6c6c8a;
  --border: rgba(108, 92, 231, 0.3);
  --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 20px rgba(108, 92, 231, 0.3);
  --radius: 16px;
  --radius-sm: 10px;
  --radius-xs: 6px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

html, body {
  height: 100%;
  overflow: hidden;
}

body {
  font-family: var(--font);
  background: var(--bg-dark);
  color: var(--text-primary);
  display: flex;
  justify-content: center;
  align-items: center;
}

body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background:
    radial-gradient(ellipse at 20% 20%, rgba(108, 92, 231, 0.15) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 80%, rgba(0, 206, 201, 0.1) 0%, transparent 50%),
    radial-gradient(ellipse at 50% 50%, rgba(253, 203, 110, 0.05) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
}

#app {
  width: 100%;
  max-width: 800px;
  height: 100vh;
  max-height: 100vh;
  position: relative;
  overflow: hidden;
  z-index: 1;
}

.screen {
  display: none;
  width: 100%;
  height: 100%;
  overflow-y: auto;
  padding: 20px;
  animation: fadeIn 0.4s ease;
}

.screen.active {
  display: flex;
  flex-direction: column;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-10px); }
  40% { transform: translateX(10px); }
  60% { transform: translateX(-10px); }
  80% { transform: translateX(10px); }
}

@keyframes bounceIn {
  0% { transform: scale(0); opacity: 0; }
  50% { transform: scale(1.15); }
  100% { transform: scale(1); opacity: 1; }
}

@keyframes shimmer {
  0% { background-position: -200% center; }
  100% { background-position: 200% center; }
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

.hidden {
  display: none !important;
}

/* Landing Screen */
.landing-container {
  max-width: 600px;
  margin: 0 auto;
  text-align: center;
  padding: 20px 0;
}

.game-title {
  font-size: 3rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), var(--secondary), var(--accent));
  background-size: 200% auto;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  animation: shimmer 3s linear infinite;
  margin-bottom: 8px;
  letter-spacing: -1px;
}

.title-icon {
  -webkit-text-fill-color: var(--accent);
  font-size: 2rem;
  animation: float 2s ease-in-out infinite;
  display: inline-block;
}

.game-subtitle {
  color: var(--text-secondary);
  font-size: 1.1rem;
  margin-bottom: 30px;
}

.form-group {
  margin-bottom: 24px;
  text-align: left;
}

.form-group label {
  display: block;
  margin-bottom: 8px;
  font-weight: 600;
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.form-group input {
  width: 100%;
  padding: 14px 18px;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: var(--font);
  transition: var(--transition);
  outline: none;
}

.form-group input:focus {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
}

.form-group input::placeholder {
  color: var(--text-muted);
}

.subject-selection h3,
.difficulty-selection h3,
.question-count-selection h3 {
  color: var(--text-secondary);
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 12px;
  margin-top: 24px;
  font-weight: 600;
}

.subject-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.subject-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  padding: 16px 8px;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.subject-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--primary);
  transform: translateY(-2px);
}

.subject-btn.active {
  background: linear-gradient(135deg, rgba(108, 92, 231, 0.2), rgba(0, 206, 201, 0.1));
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
}

.subject-icon {
  font-size: 1.8rem;
}

.difficulty-row {
  display: flex;
  gap: 10px;
  justify-content: center;
}

.diff-btn, .count-btn {
  padding: 10px 28px;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.diff-btn:hover, .count-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--primary);
}

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

.diff-btn[data-difficulty="easy"].active {
  background: var(--success);
  border-color: var(--success);
}

.diff-btn[data-difficulty="medium"].active {
  background: var(--warning);
  border-color: var(--warning);
  color: #333;
}

.diff-btn[data-difficulty="hard"].active {
  background: var(--error);
  border-color: var(--error);
}

.count-row {
  display: flex;
  gap: 10px;
  justify-content: center;
}

.count-btn {
  min-width: 60px;
}

.count-btn.active {
  background: var(--secondary);
  border-color: var(--secondary);
}

.start-btn {
  margin-top: 30px;
  padding: 18px 50px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  border: none;
  border-radius: var(--radius);
  color: var(--text-primary);
  font-family: var(--font);
  font-size: 1.25rem;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
  box-shadow: var(--shadow-glow);
  letter-spacing: 0.5px;
}

.start-btn:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 40px rgba(108, 92, 231, 0.5);
}

.start-btn:active {
  transform: translateY(-1px);
}

.high-scores-landing {
  margin-top: 30px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

.high-scores-landing h3 {
  color: var(--text-secondary);
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 12px;
}

.mini-leaderboard {
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 14px;
  text-align: left;
}

.leaderboard-entry {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 12px;
  border-bottom: 1px solid rgba(108, 92, 231, 0.1);
  font-size: 0.9rem;
}

.leaderboard-entry:last-child {
  border-bottom: none;
}

.leaderboard-entry .rank {
  color: var(--accent);
  font-weight: 700;
  min-width: 30px;
}

.leaderboard-entry .name {
  flex: 1;
  color: var(--text-secondary);
  margin-left: 8px;
}

.leaderboard-entry .score {
  font-weight: 700;
  color: var(--secondary);
}

.leaderboard-entry .badge {
  margin-left: 8px;
  font-size: 0.8rem;
}

/* Game Screen */
.game-header {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 12px 16px;
  margin-bottom: 16px;
  border: 1px solid var(--border);
}

.player-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

#hud-player {
  font-weight: 700;
  color: var(--text-primary);
}

#hud-subject {
  color: var(--text-muted);
  font-size: 0.85rem;
  padding: 2px 10px;
  background: rgba(108, 92, 231, 0.15);
  border-radius: 20px;
}

.score-timer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.timer-container {
  position: relative;
  display: flex;
  align-items: center;
  gap: 8px;
}

#timer-text {
  font-weight: 700;
  font-size: 1.3rem;
  min-width: 36px;
  text-align: center;
  color: var(--text-primary);
}

.timer-bar-container {
  flex: 1;
  max-width: 200px;
  height: 6px;
}

.timer-text {
  font-weight: 700;
  font-size: 1.3rem;
  min-width: 36px;
  text-align: center;
  color: var(--text-primary);
}

.timer-bar {
  width: 100%;
  height: 6px;
  background: linear-gradient(90deg, var(--success), var(--secondary));
  border-radius: 3px;
  transition: width 0.1s linear;
  position: relative;
}

.timer-bar.warning {
  background: linear-gradient(90deg, var(--warning), var(--error));
}

.timer-bar.danger {
  background: var(--error);
  animation: pulse 0.5s infinite;
}

.score-display {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent);
}

.score-display span:first-child {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-right: 4px;
  font-weight: 400;
}

.progress-info {
  display: flex;
  align-items: center;
  gap: 8px;
}

#progress-text {
  font-size: 0.8rem;
  color: var(--text-muted);
  min-width: 50px;
  font-weight: 600;
}

.progress-bar-bg {
  flex: 1;
  height: 4px;
  background: rgba(108, 92, 231, 0.15);
  border-radius: 2px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: 2px;
  transition: width 0.5s ease;
}

.streak-badge {
  font-size: 0.8rem;
  padding: 3px 10px;
  background: linear-gradient(135deg, rgba(253, 203, 110, 0.2), rgba(253, 203, 110, 0.1));
  border: 1px solid rgba(253, 203, 110, 0.4);
  border-radius: 20px;
  color: var(--accent);
  font-weight: 700;
}

.streak-badge.hot {
  animation: pulse 0.8s infinite;
  border-color: var(--error);
  color: var(--error);
  background: linear-gradient(135deg, rgba(225, 112, 85, 0.2), rgba(225, 112, 85, 0.1));
}

/* Question Container */
.question-container {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 28px 24px;
  margin-bottom: 16px;
  border: 1px solid var(--border);
  min-height: 120px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  text-align: center;
}

.question-badge {
  display: inline-block;
  padding: 4px 14px;
  background: rgba(108, 92, 231, 0.15);
  border-radius: 20px;
  font-size: 0.8rem;
  color: var(--primary);
  font-weight: 700;
  margin-bottom: 16px;
  align-self: center;
  text-transform: uppercase;
  letter-spacing: 1px;
}

#question-text {
  font-size: 1.25rem;
  line-height: 1.6;
  color: var(--text-primary);
  word-wrap: break-word;
}

.timer-warning {
  margin-top: 10px;
  color: var(--error);
  font-weight: 700;
  font-size: 0.9rem;
  animation: pulse 1s infinite;
}

/* Options Grid */
.options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}

.option-btn {
  padding: 18px 20px;
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  text-align: left;
  position: relative;
  overflow: hidden;
}

.option-btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, rgba(108, 92, 231, 0.1), rgba(0, 206, 201, 0.05));
  opacity: 0;
  transition: var(--transition);
}

.option-btn:hover:not(.disabled) {
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

.option-btn:hover:not(.disabled)::before {
  opacity: 1;
}

.option-btn .option-letter {
  display: inline-block;
  width: 28px;
  height: 28px;
  line-height: 28px;
  text-align: center;
  background: rgba(108, 92, 231, 0.2);
  border-radius: 50%;
  margin-right: 12px;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--primary);
}

.option-btn.correct {
  border-color: var(--success);
  background: rgba(0, 184, 148, 0.15);
  animation: bounceIn 0.4s;
}

.option-btn.correct .option-letter {
  background: var(--success);
  color: white;
}

.option-btn.wrong {
  border-color: var(--error);
  background: rgba(225, 112, 85, 0.15);
  animation: shake 0.5s;
}

.option-btn.wrong .option-letter {
  background: var(--error);
  color: white;
}

.option-btn.disabled {
  cursor: default;
  opacity: 0.6;
}

.option-btn.disabled.correct {
  opacity: 1;
}

/* Explanation Box */
.explanation-box {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 20px;
  border: 1px solid var(--border);
  animation: slideUp 0.4s ease;
  text-align: center;
  margin-bottom: 12px;
}

.explanation-text {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
  margin-bottom: 14px;
}

.next-btn {
  padding: 12px 32px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  border: none;
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
}

.next-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

/* Feedback Overlay */
.feedback-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 100;
  pointer-events: none;
  background: rgba(0, 0, 0, 0.6);
}

.feedback-icon {
  font-size: 5rem;
  animation: bounceIn 0.4s;
  margin-bottom: 16px;
}

.feedback-text {
  font-size: 1.5rem;
  font-weight: 800;
  animation: bounceIn 0.5s;
}

.feedback-overlay.correct-fb .feedback-icon { color: var(--success); }
.feedback-overlay.correct-fb .feedback-text { color: var(--success); }
.feedback-overlay.wrong-fb .feedback-icon { color: var(--error); }
.feedback-overlay.wrong-fb .feedback-text { color: var(--error); }
.feedback-overlay.timeout-fb .feedback-icon { color: var(--warning); }
.feedback-overlay.timeout-fb .feedback-text { color: var(--warning); }

/* Results Screen */
.results-container {
  max-width: 500px;
  margin: 0 auto;
  text-align: center;
  padding: 20px 0;
}

.results-title {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 24px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.results-score-circle {
  position: relative;
  width: 200px;
  height: 200px;
  margin: 0 auto 24px;
}

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

.ring-bg {
  fill: none;
  stroke: rgba(108, 92, 231, 0.15);
  stroke-width: 12;
}

.ring-progress {
  fill: none;
  stroke: url(#scoreGradient);
  stroke-width: 12;
  stroke-linecap: round;
  stroke-dasharray: 534;
  stroke-dashoffset: 534;
  transition: stroke-dashoffset 1.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.result-percentage {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 2.5rem;
  font-weight: 800;
}

.results-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-bottom: 20px;
}

.stat-card {
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 14px 8px;
  border: 1px solid var(--border);
}

.stat-card .stat-icon {
  font-size: 1.4rem;
  margin-bottom: 4px;
}

.stat-card.correct .stat-icon { color: var(--success); }
.stat-card.wrong .stat-icon { color: var(--error); }
.stat-card.streak .stat-icon { color: var(--warning); }
.stat-card.time .stat-icon { color: var(--secondary); }

.stat-value {
  font-size: 1.4rem;
  font-weight: 800;
  color: var(--text-primary);
}

.stat-label {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-top: 2px;
}

.new-high-score {
  background: linear-gradient(135deg, rgba(253, 203, 110, 0.2), rgba(253, 203, 110, 0.1));
  border: 2px solid var(--accent);
  border-radius: var(--radius-sm);
  padding: 12px;
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--accent);
  animation: bounceIn 0.6s;
  margin-bottom: 16px;
}

.results-score-display {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.results-score-display span {
  color: var(--accent);
  font-size: 1.6rem;
}

.results-grade {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-secondary);
  margin-bottom: 20px;
}

.results-actions {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin-bottom: 30px;
}

.play-btn, .change-btn {
  padding: 14px 30px;
  border: none;
  border-radius: var(--radius-sm);
  font-family: var(--font);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
}

.play-btn {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: var(--text-primary);
}

.play-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

.change-btn {
  background: var(--bg-card);
  color: var(--text-primary);
  border: 2px solid var(--border);
}

.change-btn:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
}

.results-leaderboard {
  border-top: 1px solid var(--border);
  padding-top: 16px;
}

.results-leaderboard h3 {
  color: var(--text-secondary);
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 12px;
}

.full-leaderboard {
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 10px;
  text-align: left;
  max-height: 200px;
  overflow-y: auto;
}

/* Loading */
.loading-container {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
  gap: 20px;
}

.loader {
  width: 50px;
  height: 50px;
  border: 4px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

/* SVG hidden gradient */
.svg-defs {
  position: absolute;
  width: 0;
  height: 0;
}

/* Scrollbar */
.screen::-webkit-scrollbar {
  width: 6px;
}

.screen::-webkit-scrollbar-track {
  background: transparent;
}

.screen::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}

/* Responsive */
@media (max-width: 600px) {
  .game-title {
    font-size: 2.2rem;
  }

  .subject-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
  }

  .subject-btn {
    padding: 12px 6px;
  }

  .subject-icon {
    font-size: 1.4rem;
  }

  .options-grid {
    grid-template-columns: 1fr;
  }

  .results-stats {
    grid-template-columns: repeat(2, 1fr);
  }

  #question-text {
    font-size: 1.05rem;
  }

  .results-score-circle {
    width: 160px;
    height: 160px;
  }

  .result-percentage {
    font-size: 2rem;
  }

  .results-actions {
    flex-direction: column;
  }
}