:root {
      color-scheme: light dark;
      --bg: #f4f7fb;
      --card: #ffffff;
      --text: #172033;
      --muted: #667085;
      --border: #d9e1ec;
      --primary: #2563eb;
      --primary-hover: #1d4ed8;
      --success: #16794a;
      --success-bg: #e9f8f0;
      --danger: #b42318;
      --danger-bg: #fff0ee;
      --shadow: 0 18px 45px rgba(23, 32, 51, 0.12);
    }

    @media (prefers-color-scheme: dark) {
      :root {
        --bg: #0f172a;
        --card: #172033;
        --text: #f8fafc;
        --muted: #b8c0cf;
        --border: #344054;
        --primary: #60a5fa;
        --primary-hover: #93c5fd;
        --success: #6ee7a8;
        --success-bg: #123f2b;
        --danger: #fda29b;
        --danger-bg: #4a1f1f;
        --shadow: 0 18px 45px rgba(0, 0, 0, 0.3);
      }
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      min-height: 100vh;
      font-family:
        Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
        "Segoe UI", sans-serif;
      background:
        radial-gradient(circle at top left, rgba(37, 99, 235, 0.14), transparent 36rem),
        var(--bg);
      color: var(--text);
    }

    main {
      width: min(760px, calc(100% - 32px));
      margin: 0 auto;
      padding: 48px 0;
    }

    .card {
      background: var(--card);
      border: 1px solid var(--border);
      border-radius: 22px;
      box-shadow: var(--shadow);
      overflow: hidden;
    }

    .header {
      padding: 28px 28px 22px;
      border-bottom: 1px solid var(--border);
    }

    h1 {
      margin: 0 0 8px;
      font-size: clamp(2rem, 7vw, 3.4rem);
      line-height: 1;
      letter-spacing: -0.045em;
    }

    .subtitle {
      margin: 0;
      color: var(--muted);
      font-size: 1.05rem;
    }

    .status-row {
      display: flex;
      justify-content: space-between;
      gap: 16px;
      margin-top: 22px;
      color: var(--muted);
      font-size: 0.95rem;
    }

    .progress-track {
      height: 9px;
      margin-top: 10px;
      border-radius: 999px;
      background: var(--border);
      overflow: hidden;
    }

    .progress-bar {
      width: 0;
      height: 100%;
      background: var(--primary);
      transition: width 220ms ease;
    }

    .content {
      padding: 28px;
    }

    .prompt {
      margin: 0 0 18px;
      font-size: 1.25rem;
      font-weight: 700;
    }

    .media-box {
      min-height: 120px;
      display: grid;
      place-items: center;
      padding: 22px;
      border: 1px dashed var(--border);
      border-radius: 16px;
      background: color-mix(in srgb, var(--card) 90%, var(--primary) 10%);
    }

    audio,
    video {
      width: 100%;
      max-height: 390px;
      border-radius: 12px;
    }

    .media-error {
      margin: 0;
      color: var(--danger);
      text-align: center;
      line-height: 1.55;
    }

    .choices {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 14px;
      margin-top: 22px;
    }

    button {
      min-height: 54px;
      border: 0;
      border-radius: 13px;
      padding: 13px 18px;
      font: inherit;
      font-weight: 750;
      cursor: pointer;
      transition:
        transform 100ms ease,
        background-color 140ms ease,
        opacity 140ms ease;
    }

    button:hover:not(:disabled) {
      transform: translateY(-1px);
    }

    button:focus-visible {
      outline: 3px solid color-mix(in srgb, var(--primary) 60%, transparent);
      outline-offset: 3px;
    }

    button:disabled {
      cursor: default;
      opacity: 0.7;
    }

    .choice {
      color: white;
      background: var(--primary);
    }

    .choice:hover:not(:disabled) {
      background: var(--primary-hover);
    }

    .secondary {
      width: 100%;
      margin-top: 14px;
      color: var(--text);
      background: transparent;
      border: 1px solid var(--border);
    }

    .feedback {
      display: none;
      margin-top: 20px;
      padding: 16px;
      border-radius: 13px;
      line-height: 1.5;
    }

    .feedback.correct {
      display: block;
      color: var(--success);
      background: var(--success-bg);
    }

    .feedback.incorrect {
      display: block;
      color: var(--danger);
      background: var(--danger-bg);
    }

    .feedback strong {
      display: block;
      margin-bottom: 3px;
      font-size: 1.05rem;
    }

    .next {
      display: none;
      width: 100%;
      margin-top: 14px;
      color: white;
      background: var(--primary);
    }

    .result {
      display: none;
      padding: 44px 28px;
      text-align: center;
    }

    .result h2 {
      margin: 0 0 12px;
      font-size: clamp(2rem, 7vw, 3rem);
    }

    .final-score {
      margin: 0 0 8px;
      font-size: 1.35rem;
      font-weight: 800;
    }

    .result-message {
      margin: 0 0 24px;
      color: var(--muted);
    }

    .small-note {
      margin: 22px 0 0;
      color: var(--muted);
      font-size: 0.88rem;
      line-height: 1.55;
    }

    code {
      padding: 0.12em 0.35em;
      border-radius: 5px;
      background: color-mix(in srgb, var(--border) 58%, transparent);
    }

    @media (max-width: 560px) {
      main {
        padding: 20px 0;
      }

      .header,
      .content {
        padding: 22px;
      }

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