:root {
  color-scheme: light dark;
  --bg: #0f172a;
  --fg: #f8fafc;
  --muted: #94a3b8;
  --accent: #38bdf8;
  --success: #22c55e;
  --danger: #ef4444;
  --card: rgba(15, 23, 42, 0.7);
  --border: rgba(148, 163, 184, 0.2);
  font-size: 16px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Inter", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: linear-gradient(160deg, #020617 0%, #0f172a 35%, #1e293b 100%);
  color: var(--fg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.page-header {
  width: 100%;
  max-width: 480px;
  padding: 24px 20px 8px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  align-items: flex-start;
}

.page-header h1 {
  margin: 0;
  font-size: clamp(1.5rem, 5vw, 2rem);
}

.difficulty-group {
  display: flex;
  gap: 8px;
  align-items: center;
}

.container {
  width: 100%;
  max-width: 480px;
  padding: 0 20px 32px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 16px;
}

.control {
  display: flex;
  flex-direction: column;
  font-size: 0.9rem;
  gap: 6px;
}

.control select,
.control input[type="number"] {
  border-radius: 12px;
  border: 1px solid var(--border);
  background: rgba(15, 23, 42, 0.6);
  color: var(--fg);
  padding: 8px 12px;
  font-size: 1rem;
}

.toggle {
  flex-direction: row;
  gap: 8px;
  align-items: center;
}

.toggle input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
}

.question-card {
  position: relative;
  display: flex;
  gap: 16px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 24px;
  padding: 24px;
  align-items: center;
}

.timer {
  position: relative;
  width: 96px;
  height: 96px;
  flex-shrink: 0;
  display: grid;
  place-items: center;
}

.timer span {
  position: absolute;
  font-weight: 600;
  font-size: 1.25rem;
}

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

.timer-track {
  fill: none;
  stroke: rgba(148, 163, 184, 0.2);
  stroke-width: 10;
}

.timer-progress {
  fill: none;
  stroke: var(--accent);
  stroke-width: 10;
  stroke-dasharray: 339.292;
  stroke-dashoffset: 0;
  transition: stroke-dashoffset 0.2s linear;
}

.question-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.question {
  font-size: clamp(1.3rem, 5vw, 1.6rem);
  font-weight: 600;
}

.answer-row {
  display: flex;
  gap: 8px;
}

.answer-row input {
  flex: 1;
  padding: 12px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: rgba(15, 23, 42, 0.8);
  color: var(--fg);
  font-size: 1.1rem;
}

.answer-row button {
  padding: 12px 18px;
  border: none;
  border-radius: 12px;
  background: var(--accent);
  color: #0f172a;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.answer-row button:hover,
.answer-row button:focus-visible {
  transform: translateY(-1px);
  box-shadow: 0 8px 20px rgba(56, 189, 248, 0.3);
}

.feedback {
  min-height: 24px;
  font-weight: 600;
}

.scoreboard {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px;
}

.score-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.score-item .label {
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--muted);
  letter-spacing: 0.06em;
}

.score-item span:last-child {
  font-size: 1.4rem;
  font-weight: 700;
}

#levelProgress {
  font-variant-numeric: tabular-nums;
  font-size: 1.3rem;
}

#level {
  line-height: 1.2;
  font-size: 1.2rem;
}

.leaderboard {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.leaderboard-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}

.leaderboard-header h2 {
  margin: 0;
  font-size: 1.1rem;
}

.leaderboard-header button {
  border: 1px solid var(--border);
  background: rgba(15, 23, 42, 0.8);
  color: var(--fg);
  border-radius: 12px;
  padding: 8px 12px;
  cursor: pointer;
}

.leaderboard-list {
  margin: 0;
  padding-left: 20px;
  display: grid;
  gap: 6px;
}

.leaderboard-list li {
  font-size: 0.95rem;
}

.muted {
  color: var(--muted);
  font-style: italic;
}

.actions {
  display: flex;
  justify-content: center;
}

.actions button {
  border: none;
  background: var(--accent);
  color: #0f172a;
  font-weight: 600;
  border-radius: 999px;
  padding: 12px 28px;
  cursor: pointer;
  transition: transform 0.2s ease;
}

.actions button:hover,
.actions button:focus-visible {
  transform: translateY(-1px);
}

.page-footer {
  margin-top: auto;
  padding: 24px 20px 40px;
  text-align: center;
  color: var(--muted);
  font-size: 0.8rem;
}

.correct {
  color: var(--success);
  animation: pulse 0.6s ease;
}

.wrong {
  color: var(--danger);
  animation: shake 0.4s ease;
}

@keyframes shake {
  10%,
  90% {
    transform: translateX(-2px);
  }
  20%,
  80% {
    transform: translateX(4px);
  }
  30%,
  50%,
  70% {
    transform: translateX(-6px);
  }
  40%,
  60% {
    transform: translateX(6px);
  }
}

@keyframes pulse {
  0% {
    transform: scale(0.95);
  }
  50% {
    transform: scale(1.05);
  }
  100% {
    transform: scale(1);
  }
}

@media (min-width: 600px) {
  body {
    justify-content: center;
  }

  .page-header,
  .container {
    max-width: 520px;
  }
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}