:root {
  --black: #1a1a1a;
  --white: #fafafa;
  --bg: #2b2d42;
  --bg-dark: #1e1f33;
  --yellow: #FFDE59;
  --red: #FF5757;
  --blue: #3B82F6;
  --green: #4ADE80;
  --pink: #F472B6;
  --orange: #FB923C;
  --cyan: #22D3EE;
  --border: 3px solid var(--black);
  --border-thick: 4px solid var(--black);
  --shadow: 5px 5px 0 var(--black);
  --shadow-sm: 3px 3px 0 var(--black);
  --shadow-lg: 7px 7px 0 var(--black);
  --radius: 12px;
  --radius-sm: 8px;
  --font-heading: 'Fredoka', sans-serif;
  --font-body: 'Nunito', sans-serif;
}

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

body {
  font-family: var(--font-body);
  background: var(--bg-dark);
  color: var(--white);
  overflow: hidden;
  width: 100vw;
  height: 100vh;
  user-select: none;
  -webkit-user-select: none;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  overscroll-behavior: contain;
  color-scheme: dark;
}

/* ========== OVERLAYS ========== */
.overlay {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  overscroll-behavior: contain;
}
.overlay.active {
  display: flex;
}
.overlay-inner {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 50;
}
.overlay-inner.hidden {
  display: none;
}

/* ========== LOADING ========== */
#loadingOverlay {
  background: var(--bg-dark);
  gap: 20px;
}
.loading-box {
  text-align: center;
  background: var(--bg);
  border: var(--border-thick);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  padding: 40px 60px;
}
.loading-spinner {
  width: 50px;
  height: 50px;
  border: 5px solid var(--blue);
  border-top-color: var(--yellow);
  border-radius: 50%;
  margin: 0 auto 16px;
  animation: spin 0.8s linear infinite;
}
.loading-text {
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--yellow);
}

/* ========== START SCREEN ========== */
#startScreen {
  background: var(--bg-dark);
  padding: 20px;
}
.start-content {
  text-align: center;
  max-width: 480px;
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 24px;
}
.title-block {
  padding: 30px 20px 20px;
}
.game-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: clamp(3rem, 10vw, 5rem);
  line-height: 1;
  color: var(--yellow);
  text-shadow: 4px 4px 0 var(--black);
  letter-spacing: 2px;
}
.game-subtitle {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 1rem;
  color: var(--cyan);
  margin-top: 12px;
}

/* Difficulty */
.diff-label {
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 1rem;
  color: var(--white);
  margin-bottom: 10px;
}
.diff-cards {
  display: flex;
  gap: 12px;
  justify-content: center;
}
.diff-card {
  background: var(--bg);
  border: var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  padding: 14px 12px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  cursor: pointer;
  transition: transform 0.1s, box-shadow 0.1s;
  flex: 1;
  min-width: 110px;
  color: var(--white);
}
.diff-card:hover {
  transform: translate(2px, 2px);
  box-shadow: 1px 1px 0 var(--black);
}
.diff-card.selected {
  background: var(--yellow);
  color: var(--black);
  transform: translate(3px, 3px);
  box-shadow: 0 0 0 var(--black);
}
.diff-card.selected .diff-desc {
  color: var(--bg-dark);
}
.diff-icon {
  font-size: 1.8rem;
}
.diff-name {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.95rem;
}
.diff-desc {
  font-size: 0.7rem;
  font-weight: 600;
  opacity: 0.8;
}

/* Gesture hint */
.gesture-hint {
  background: var(--bg);
  border: var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  padding: 14px 18px;
  font-size: 0.8rem;
  font-weight: 600;
  line-height: 1.6;
  color: var(--cyan);
}

/* Start button */
.btn-start {
  display: block;
  width: 100%;
  padding: 16px 32px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.3rem;
  background: var(--green);
  color: var(--black);
  border: var(--border-thick);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  cursor: pointer;
  transition: transform 0.1s, box-shadow 0.1s;
}
.btn-start:hover {
  transform: translate(2px, 2px);
  box-shadow: var(--shadow-sm);
}
.btn-start:active {
  transform: translate(4px, 4px);
  box-shadow: none;
}
.btn-start:focus-visible,
.btn-menu:focus-visible,
.diff-card:focus-visible,
.math-option:focus-visible {
  outline: 3px solid var(--cyan);
  outline-offset: 2px;
}
.btn-menu {
  display: block;
  width: 100%;
  padding: 14px 32px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.1rem;
  background: var(--bg);
  color: var(--white);
  border: var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  transition: transform 0.1s, box-shadow 0.1s;
}
.btn-menu:hover {
  transform: translate(2px, 2px);
  box-shadow: 1px 1px 0 var(--black);
}

/* ========== GAME SCREEN ========== */
#gameScreen {
  z-index: 10;
  background: #0a0a1a;
}
#gameScreen.active {
  display: block;
}
#video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
  object-fit: cover;
  pointer-events: none;
  transform: scaleX(-1);
}
#gameScreen::after {
  content: '';
  position: absolute;
  inset: 0;
  z-index: 2;
  background: rgba(10, 10, 26, 0.35);
  pointer-events: none;
}
#gameCanvas {
  display: block;
  width: 100%;
  height: 100%;
  position: relative;
  z-index: 3;
}

/* ========== HUD ========== */
.hud {
  position: absolute;
  top: env(safe-area-inset-top, 0);
  left: env(safe-area-inset-left, 0);
  right: env(safe-area-inset-right, 0);
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  padding: 12px 16px;
  z-index: 300;
  pointer-events: none;
}
.hud-left, .hud-right {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.hud-center {
  text-align: center;
}
.hud-item {
  background: var(--bg);
  border: var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  padding: 8px 12px;
  pointer-events: auto;
}
.hud-label {
  display: block;
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 0.65rem;
  color: var(--yellow);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 4px;
}
.hud-value {
  display: block;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.3rem;
}
.bar-wrap {
  width: 120px;
  height: 12px;
  background: var(--bg-dark);
  border: 2px solid var(--black);
  border-radius: 4px;
  overflow: hidden;
  flex: 1;
}
.bar-row {
  display: flex;
  align-items: center;
  gap: 8px;
}
.bar-row .hud-value {
  font-size: 0.85rem;
  min-width: 28px;
  text-align: right;
}
.bar-fill {
  height: 100%;
  width: 100%;
  background: var(--blue);
  transform-origin: left;
  transition: transform 0.15s;
  border-radius: 2px;
}
.bar-fill.fuel {
  background: var(--green);
}
.bar-fill.fuel.low {
  background: var(--orange);
}
.bar-fill.fuel.critical {
  background: var(--red);
  animation: pulse 0.5s infinite;
}
.hud-zone {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--cyan);
  background: var(--bg);
  border: var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  padding: 6px 18px;
  opacity: 0.9;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 160px;
}
.hud-lives {
  display: flex;
  gap: 4px;
  font-size: 1.1rem;
}
.hud-score .hud-value {
  color: var(--yellow);
}

/* ========== COUNTDOWN ========== */
.countdown-num {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 6rem;
  color: var(--yellow);
  text-shadow: 4px 4px 0 var(--black);
  animation: countPulse 0.5s ease-out;
}

/* ========== MATH OVERLAY ========== */
.math-box {
  background: var(--bg);
  border: var(--border-thick);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  padding: 24px 32px;
  text-align: center;
  min-width: 320px;
  max-width: 90vw;
}
.math-label {
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--cyan);
  margin-bottom: 10px;
}
.math-question {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 2rem;
  color: var(--yellow);
  margin-bottom: 16px;
}
.math-options {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
}
.math-option {
  padding: 10px 20px;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.2rem;
  background: var(--bg-dark);
  color: var(--white);
  border: var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  transition: transform 0.1s, box-shadow 0.1s;
  min-width: 70px;
}
.math-option:hover {
  background: var(--blue);
  color: var(--white);
  transform: translate(2px, 2px);
  box-shadow: 1px 1px 0 var(--black);
}
.math-option.highlighted {
  background: var(--cyan);
  color: var(--black);
  transform: scale(1.1);
  box-shadow: 0 0 20px var(--cyan);
}
.math-option.correct {
  background: var(--green);
  color: var(--black);
}
.math-option.wrong {
  background: var(--red);
  color: var(--white);
}
.math-timer {
  margin-top: 16px;
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--white);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
}
.math-timer-icon {
  font-size: 1rem;
}
#mathTimer {
  color: var(--cyan);
  font-size: 1.6rem;
  min-width: 2ch;
  text-align: center;
}
#mathTimer.urgent {
  color: var(--red);
  animation: pulse 0.5s infinite;
}
.math-timer-unit {
  font-size: 1rem;
  opacity: 0.7;
}

/* ========== GAME OVER ========== */
#gameOverScreen {
  background: rgba(10, 10, 26, 0.92);
  backdrop-filter: blur(4px);
  padding: 20px;
}
.gameover-content {
  text-align: center;
  max-width: 420px;
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.gameover-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 2.8rem;
  color: var(--red);
  text-shadow: 3px 3px 0 var(--black);
}
.gameover-card {
  background: var(--bg);
  border: var(--border-thick);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  padding: 24px;
}
.gameover-score {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 3rem;
  color: var(--yellow);
  margin-bottom: 12px;
}
.gameover-stats {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--cyan);
  line-height: 1.8;
}
.gameover-leaderboard {
  background: var(--bg);
  border: var(--border);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-sm);
  padding: 16px 20px;
}
.gameover-leaderboard h3 {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1rem;
  color: var(--yellow);
  margin-bottom: 10px;
}
.gameover-leaderboard ol {
  list-style: none;
  counter-reset: lb;
}
.gameover-leaderboard li {
  counter-increment: lb;
  padding: 4px 0;
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--white);
  display: flex;
  justify-content: space-between;
  border-bottom: 2px solid var(--bg-dark);
}
.gameover-leaderboard li:last-child {
  border-bottom: none;
}
.gameover-leaderboard li::before {
  content: counter(lb) ". ";
  color: var(--yellow);
  font-weight: 700;
}
.gameover-buttons {
  display: flex;
  gap: 12px;
}
.gameover-buttons .btn-start {
  flex: 2;
}
.gameover-buttons .btn-menu {
  flex: 1;
}

/* ========== GAME STATUS ========== */
.game-status {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 400;
  pointer-events: none;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 2rem;
  color: var(--yellow);
  text-shadow: 3px 3px 0 var(--black);
  opacity: 0;
  transition: opacity 0.3s;
}
.game-status.show {
  opacity: 1;
}

/* ========== ANIMATIONS ========== */
@keyframes spin {
  to { transform: rotate(360deg); }
}
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}
@keyframes countPulse {
  0% { transform: scale(1.8); opacity: 0.3; }
  100% { transform: scale(1); opacity: 1; }
}
@keyframes slideUp {
  from { transform: translateY(30px); opacity: 0; }
  to { transform: translateY(0); opacity: 1; }
}

/* ========== RESPONSIVE ========== */
@media (max-width: 600px) {
  .game-title {
    font-size: 3rem;
  }
  .diff-cards {
    flex-direction: column;
    align-items: center;
  }
  .diff-card {
    min-width: 200px;
  }
  .bar-wrap {
    width: 90px;
  }
  .hud {
    padding: 8px 10px;
  }
  .hud-item {
    padding: 6px 8px;
  }
  .math-box {
    min-width: auto;
    padding: 20px 16px;
  }
  .math-question {
    font-size: 1.5rem;
  }
  .countdown-num {
    font-size: 4rem;
  }
  .gameover-score {
    font-size: 2.2rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}