:root {
        color-scheme: light;
        --ink: #2d2431;
        --muted: #756c79;
        --line: #e2d8e7;
        --surface: #ffffff;
        --surface-soft: #f5eff8;
        --page: #f7f3f9;
        --primary: #9300D3;
        --primary-dark: #650094;
        --primary-soft: #f0dcfa;
        --success: #7c27b5;
        --success-soft: #f3e6fa;
        --danger: #b14e52;
        --danger-soft: #fceced;
        --warning: #9b681e;
        --warning-soft: #fff6e4;
        --purple: #8b45b5;
        --shadow: 0 5px 18px rgba(70, 28, 86, 0.11);
      }

      .skip-link {
        position: absolute;
        top: -9999px;
        left: 1rem;
        z-index: 10000;
        padding: 0.75rem 1.25rem;
        background: #111;
        color: #fff;
        font-size: 0.95rem;
        font-weight: 600;
        text-decoration: none;
        border-radius: 4px;
        box-shadow: 0 4px 12px rgba(0,0,0,0.3);
        transition: top 0.2s ease-in-out;
      }
      .skip-link:focus,
      .skip-link:focus-visible {
        top: 1rem;
        outline: 2px solid #00c8ff;
        outline-offset: 2px;
      }

      * {
        box-sizing: border-box;
      }

      body {
        min-width: 0;
        margin: 0;
        background:
          radial-gradient(circle at 50% -20%, #f1e2f8 0, transparent 38rem),
          var(--page);
        color: var(--ink);
        font-family: Arial, sans-serif;
      }

      button,
      select {
        font: inherit;
      }

      button,
      a {
        -webkit-tap-highlight-color: transparent;
      }

      button:focus-visible,
      a:focus-visible,
      select:focus-visible {
        outline: 3px solid rgba(147, 0, 211, 0.3);
        outline-offset: 2px;
      }

      [hidden] {
        display: none !important;
      }

      .topbar {
        position: sticky;
        top: 0;
        z-index: 20;
        border-bottom: 1px solid rgba(220, 207, 226, 0.92);
        background: rgba(255, 255, 255, 0.9);
        backdrop-filter: blur(14px);
      }

      .topbar-inner {
        display: flex;
        width: min(94%, 1200px);
        min-height: 64px;
        align-items: center;
        justify-content: space-between;
        gap: 18px;
        margin: auto;
      }

      .brand {
        display: inline-flex;
        min-width: 0;
        align-items: center;
        gap: 10px;
        color: var(--ink);
        text-decoration: none;
      }

      .brand-mark {
        display: grid;
        width: 38px;
        height: 38px;
        flex: 0 0 auto;
        place-items: center;
        border: 1px solid #c797dc;
        border-radius: 11px;
        background: linear-gradient(135deg, #f2dffc, #ead8f4);
        color: var(--primary-dark);
        font-size: 1.3rem;
        box-shadow: 0 3px 9px rgba(94, 29, 120, 0.12);
      }

      .brand-copy {
        min-width: 0;
      }

      .brand-copy strong,
      .brand-copy span {
        display: block;
      }

      .brand-copy strong {
        font-size: 0.9rem;
      }

      .brand-copy span {
        margin-top: 1px;
        color: var(--muted);
        font-size: 0.64rem;
      }

      .top-stats {
        display: flex;
        align-items: center;
        gap: 7px;
      }

      .top-stat {
        min-width: 76px;
        padding: 6px 9px;
        border: 1px solid #e4dae9;
        border-radius: 9px;
        background: #fff;
        text-align: center;
      }

      .top-stat span,
      .top-stat strong {
        display: block;
      }

      .top-stat span {
        color: var(--muted);
        font-size: 0.56rem;
        font-weight: 700;
        letter-spacing: 0.04em;
        text-transform: uppercase;
      }

      .top-stat strong {
        margin-top: 2px;
        color: var(--primary-dark);
        font-size: 0.84rem;
      }

      .app-shell {
        width: min(94%, 1200px);
        margin: 0 auto;
        padding: 32px 0 46px;
      }

      .screen {
        animation: screen-in 320ms ease both;
      }

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

      .hero {
        display: grid;
        grid-template-columns: minmax(0, 1.2fr) minmax(310px, 0.8fr);
        gap: 18px;
        align-items: stretch;
        margin-bottom: 18px;
      }

      .hero-main,
      .progress-card,
      .mode-card,
      .difficulty-card,
      .question-card,
      .game-toolbar,
      .result-card,
      .mastery-card {
        border: 1px solid var(--line);
        border-radius: 14px;
        background: rgba(255, 255, 255, 0.96);
        box-shadow: var(--shadow);
      }

      .hero-main {
        position: relative;
        overflow: hidden;
        padding: clamp(24px, 4vw, 42px);
        background:
          linear-gradient(135deg, rgba(243, 224, 252, 0.94), #fff 62%);
      }

      .hero-main::after {
        position: absolute;
        right: -42px;
        bottom: -70px;
        width: 220px;
        height: 220px;
        border: 22px solid rgba(147, 0, 211, 0.08);
        border-radius: 50%;
        content: "";
      }

      .eyebrow {
        display: inline-flex;
        align-items: center;
        gap: 6px;
        color: var(--primary);
        font-size: 0.68rem;
        font-weight: 800;
        letter-spacing: 0.08em;
        text-transform: uppercase;
      }

      .eyebrow::before {
        width: 7px;
        height: 7px;
        border-radius: 2px;
        background: currentColor;
        content: "";
      }

      h1 {
        max-width: 680px;
        margin: 10px 0 12px;
        font-size: clamp(2rem, 5vw, 3.5rem);
        letter-spacing: -0.045em;
        line-height: 0.98;
      }

      .hero-main p {
        position: relative;
        z-index: 1;
        max-width: 640px;
        margin: 0;
        color: #675c6c;
        font-size: 0.93rem;
        line-height: 1.55;
      }

      .progress-card {
        display: flex;
        flex-direction: column;
        justify-content: space-between;
        padding: 22px;
      }

      .progress-card-header {
        display: flex;
        align-items: flex-start;
        justify-content: space-between;
        gap: 12px;
      }

      .progress-card h2,
      .section-heading h2,
      .mastery-heading h2 {
        margin: 0;
        font-size: 1rem;
      }

      .progress-card p,
      .section-heading p,
      .mastery-heading p {
        margin: 4px 0 0;
        color: var(--muted);
        font-size: 0.7rem;
        line-height: 1.4;
      }

      .level-orb {
        display: grid;
        width: 58px;
        height: 58px;
        flex: 0 0 auto;
        place-items: center;
        border: 6px solid #e8d8ef;
        border-radius: 50%;
        background: #fcf9fd;
        color: var(--primary-dark);
        font-size: 1.15rem;
        font-weight: 800;
      }

      .xp-row {
        display: flex;
        align-items: center;
        justify-content: space-between;
        gap: 12px;
        margin-top: 24px;
        color: var(--muted);
        font-size: 0.65rem;
      }

      .xp-row strong {
        color: var(--ink);
      }

      .progress-track {
        height: 9px;
        margin-top: 7px;
        overflow: hidden;
        border-radius: 999px;
        background: #e9e0ed;
      }

      .progress-fill {
        display: block;
        width: var(--progress, 0%);
        height: 100%;
        border-radius: inherit;
        background: linear-gradient(90deg, #c15be9, var(--primary));
        transition: width 380ms ease;
      }

      .progress-metrics {
        display: grid;
        grid-template-columns: repeat(3, 1fr);
        gap: 7px;
        margin-top: 18px;
      }

      .progress-metric {
        padding: 9px 6px;
        border-radius: 9px;
        background: var(--surface-soft);
        text-align: center;
      }

      .progress-metric strong,
      .progress-metric span {
        display: block;
      }

      .progress-metric strong {
        font-size: 0.9rem;
      }

      .progress-metric span {
        margin-top: 2px;
        color: var(--muted);
        font-size: 0.55rem;
      }

      .section-heading {
        display: flex;
        align-items: flex-end;
        justify-content: space-between;
        gap: 18px;
        margin: 26px 0 11px;
      }

      .difficulty-card {
        display: flex;
        align-items: center;
        gap: 5px;
        padding: 5px;
        box-shadow: none;
      }

      .difficulty-button {
        padding: 7px 10px;
        border: 0;
        border-radius: 8px;
        background: transparent;
        color: var(--muted);
        cursor: pointer;
        font-size: 0.66rem;
        font-weight: 750;
      }

      .difficulty-button:hover {
        background: #f5eff8;
        color: var(--ink);
      }

      .difficulty-button.is-active {
        background: var(--primary-soft);
        color: var(--primary-dark);
      }

      .mode-grid {
        display: grid;
        grid-template-columns: repeat(3, minmax(0, 1fr));
        gap: 12px;
      }

      .mode-card {
        position: relative;
        min-width: 0;
        overflow: hidden;
        padding: 20px;
        text-align: left;
        transition:
          transform 180ms ease,
          box-shadow 180ms ease,
          border-color 180ms ease;
      }

      button.mode-card {
        color: inherit;
        cursor: pointer;
      }

      .mode-card:hover {
        border-color: #c38cda;
        box-shadow: 0 10px 28px rgba(94, 27, 121, 0.14);
        transform: translateY(-3px);
      }

      .mode-icon {
        display: grid;
        width: 42px;
        height: 42px;
        place-items: center;
        border-radius: 11px;
        background: var(--primary-soft);
        color: var(--primary-dark);
        font-size: 1.2rem;
      }

      .mode-card[data-mode="time"] .mode-icon {
        background: var(--warning-soft);
        color: var(--warning);
      }

      .mode-card[data-mode="expedition"] .mode-icon {
        background: #eee9fa;
        color: var(--purple);
      }

      .mode-card h3 {
        margin: 14px 0 5px;
        font-size: 0.92rem;
      }

      .mode-card p {
        min-height: 3.5em;
        margin: 0;
        color: var(--muted);
        font-size: 0.69rem;
        line-height: 1.45;
      }

      .mode-meta {
        display: flex;
        align-items: center;
        justify-content: space-between;
        gap: 8px;
        margin-top: 15px;
        padding-top: 12px;
        border-top: 1px solid #f0e8f3;
        color: var(--muted);
        font-size: 0.61rem;
        font-weight: 700;
      }

      .mode-meta strong {
        color: var(--primary-dark);
      }

      .mastery-card {
        margin-top: 18px;
        padding: 18px;
      }

      .mastery-heading {
        display: flex;
        align-items: flex-start;
        justify-content: space-between;
        gap: 16px;
        margin-bottom: 13px;
      }

      .mastery-count {
        flex: 0 0 auto;
        color: var(--primary-dark);
        font-size: 0.75rem;
        font-weight: 800;
      }

      .mini-periodic-table {
        display: grid;
        grid-template-columns: repeat(18, 1fr);
        gap: 3px;
      }

      .mastery-cell {
        position: relative;
        display: grid;
        height: clamp(14px, 2.2vw, 26px);
        place-items: center;
        border: 1px solid #e2d8e7;
        border-radius: 3px;
        background: #f1ebf3;
        color: #928797;
        font-size: clamp(0.42rem, 0.7vw, 0.58rem);
        font-weight: 800;
      }

      .mastery-cell.is-mastered {
        border-color: #a84bcf;
        background: #dfb6ef;
        color: #5f087f;
        box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.45);
      }

      .mastery-cell.is-empty {
        border-color: transparent;
        background: transparent;
      }

      .game-toolbar {
        padding: 15px 17px;
      }

      .game-toolbar-main {
        display: flex;
        align-items: center;
        justify-content: space-between;
        gap: 16px;
      }

      .game-identity {
        display: flex;
        min-width: 0;
        align-items: center;
        gap: 10px;
      }

      .icon-button {
        display: grid;
        width: 36px;
        height: 36px;
        flex: 0 0 auto;
        place-items: center;
        border: 1px solid #ddd1e2;
        border-radius: 9px;
        background: #fff;
        color: var(--ink);
        cursor: pointer;
      }

      .icon-button:hover {
        background: var(--surface-soft);
      }

      .game-identity strong,
      .game-identity span {
        display: block;
      }

      .game-identity strong {
        font-size: 0.84rem;
      }

      .game-identity span {
        margin-top: 2px;
        color: var(--muted);
        font-size: 0.62rem;
      }

      .live-stats {
        display: flex;
        align-items: center;
        gap: 7px;
      }

      .live-stat {
        min-width: 78px;
        padding: 7px 10px;
        border-radius: 9px;
        background: var(--surface-soft);
        text-align: center;
      }

      .live-stat span,
      .live-stat strong {
        display: block;
      }

      .live-stat span {
        color: var(--muted);
        font-size: 0.54rem;
        font-weight: 700;
        text-transform: uppercase;
      }

      .live-stat strong {
        margin-top: 2px;
        font-size: 0.83rem;
      }

      .live-stat.is-hot {
        background: var(--warning-soft);
        color: var(--warning);
      }

      .game-progress {
        margin-top: 13px;
      }

      .game-progress .progress-track {
        height: 6px;
        margin: 0;
      }

      .question-card {
        width: min(100%, 900px);
        margin: 18px auto 0;
        padding: clamp(18px, 4vw, 30px);
      }

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

      .question-tags {
        display: flex;
        flex-wrap: wrap;
        gap: 6px;
      }

      .question-tag {
        padding: 4px 8px;
        border-radius: 999px;
        background: var(--primary-soft);
        color: var(--primary-dark);
        font-size: 0.59rem;
        font-weight: 800;
      }

      .question-tag[data-level="advanced"] {
        background: #eee9fa;
        color: var(--purple);
      }

      .question-tag[data-level="intermediate"] {
        background: var(--warning-soft);
        color: var(--warning);
      }

      .available-points {
        flex: 0 0 auto;
        color: var(--muted);
        font-size: 0.64rem;
      }

      .available-points strong {
        color: var(--primary-dark);
      }

      .question-text {
        max-width: 760px;
        margin: 22px 0 18px;
        font-size: clamp(1.25rem, 3vw, 1.75rem);
        line-height: 1.2;
      }

      .quoted-clue {
        margin: -5px 0 18px;
        padding: 12px 14px;
        border-left: 3px solid var(--primary);
        border-radius: 0 9px 9px 0;
        background: #f7f0fa;
        color: #5f5364;
        font-size: 0.78rem;
        line-height: 1.5;
      }

      .clue-area {
        margin-bottom: 16px;
      }

      .clue-list {
        display: grid;
        gap: 6px;
        margin: 0 0 9px;
        padding: 0;
        list-style: none;
      }

      .clue-list li {
        padding: 8px 10px;
        border: 1px solid #e6daeb;
        border-radius: 8px;
        background: #fbf8fc;
        color: #655a69;
        font-size: 0.7rem;
        animation: clue-in 220ms ease both;
      }

      @keyframes clue-in {
        from {
          opacity: 0;
          transform: translateX(-5px);
        }
      }

      .secondary-button,
      .primary-button {
        border-radius: 9px;
        cursor: pointer;
        font-weight: 750;
      }

      .secondary-button {
        padding: 8px 12px;
        border: 1px solid #ddd0e3;
        background: #fff;
        color: #594d5e;
        font-size: 0.68rem;
      }

      .secondary-button:hover {
        background: var(--surface-soft);
      }

      .answer-grid {
        display: grid;
        grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 9px;
      }

      .answer-button {
        position: relative;
        min-height: 58px;
        padding: 12px 44px 12px 14px;
        border: 1px solid #e1d6e5;
        border-radius: 10px;
        background: #fff;
        color: #392e3d;
        cursor: pointer;
        font-size: 0.78rem;
        font-weight: 700;
        line-height: 1.35;
        text-align: left;
        transition:
          border-color 150ms ease,
          background 150ms ease,
          transform 150ms ease;
      }

      .answer-button::after {
        position: absolute;
        top: 50%;
        right: 13px;
        display: grid;
        width: 24px;
        height: 24px;
        place-items: center;
        border: 1px solid #e2d8e7;
        border-radius: 50%;
        color: #918696;
        content: attr(data-key);
        font-size: 0.6rem;
        transform: translateY(-50%);
      }

      .answer-button:hover:not(:disabled) {
        border-color: #b667d5;
        background: #faf2fd;
        transform: translateY(-1px);
      }

      .answer-button:disabled {
        cursor: default;
      }

      .answer-button.is-correct {
        border-color: #a64bcd;
        background: var(--success-soft);
        color: #650094;
      }

      .answer-button.is-correct::after {
        border-color: var(--success);
        background: var(--success);
        color: #fff;
        content: "✓";
      }

      .answer-button.is-wrong {
        border-color: #d88a8d;
        background: var(--danger-soft);
        color: #813438;
      }

      .answer-button.is-wrong::after {
        border-color: var(--danger);
        background: var(--danger);
        color: #fff;
        content: "×";
      }

      .feedback {
        display: grid;
        grid-template-columns: auto minmax(0, 1fr) auto;
        gap: 11px;
        align-items: center;
        margin-top: 14px;
        padding: 12px;
        border: 1px solid #dcc5e7;
        border-radius: 10px;
        background: var(--success-soft);
      }

      .feedback.is-wrong {
        border-color: #ecd1d2;
        background: var(--danger-soft);
      }

      .feedback-icon {
        display: grid;
        width: 34px;
        height: 34px;
        place-items: center;
        border-radius: 50%;
        background: var(--success);
        color: #fff;
        font-weight: 800;
      }

      .feedback.is-wrong .feedback-icon {
        background: var(--danger);
      }

      .feedback-copy strong,
      .feedback-copy span {
        display: block;
      }

      .feedback-copy strong {
        font-size: 0.76rem;
      }

      .feedback-copy span {
        margin-top: 3px;
        color: #655a69;
        font-size: 0.67rem;
        line-height: 1.4;
      }

      .earned-points {
        color: var(--success);
        font-size: 0.82rem;
        font-weight: 800;
        white-space: nowrap;
      }

      .feedback.is-wrong .earned-points {
        color: var(--danger);
      }

      .question-actions {
        display: flex;
        justify-content: flex-end;
        margin-top: 13px;
      }

      .primary-button {
        padding: 10px 17px;
        border: 0;
        background: var(--primary);
        color: #fff;
        font-size: 0.72rem;
      }

      .primary-button:hover {
        background: var(--primary-dark);
      }

      .result-card {
        width: min(100%, 720px);
        margin: 20px auto 0;
        padding: clamp(24px, 5vw, 42px);
        text-align: center;
      }

      .result-medal {
        display: grid;
        width: 82px;
        height: 82px;
        margin: 0 auto;
        place-items: center;
        border: 7px solid #e8d8ef;
        border-radius: 50%;
        background: #fcf8fd;
        font-size: 2rem;
      }

      .result-card h1 {
        margin: 18px auto 8px;
        font-size: clamp(1.7rem, 5vw, 2.5rem);
      }

      .result-subtitle {
        margin: 0;
        color: var(--muted);
        font-size: 0.78rem;
      }

      .result-score {
        margin: 22px 0;
        color: var(--primary-dark);
        font-size: clamp(2.1rem, 7vw, 3.5rem);
        font-weight: 800;
        line-height: 1;
      }

      .result-score span {
        display: block;
        margin-top: 6px;
        color: var(--muted);
        font-size: 0.62rem;
        font-weight: 700;
        letter-spacing: 0.06em;
        text-transform: uppercase;
      }

      .result-grid {
        display: grid;
        grid-template-columns: repeat(3, 1fr);
        gap: 8px;
        margin-bottom: 22px;
      }

      .result-metric {
        padding: 13px 8px;
        border-radius: 10px;
        background: var(--surface-soft);
      }

      .result-metric strong,
      .result-metric span {
        display: block;
      }

      .result-metric strong {
        font-size: 1rem;
      }

      .result-metric span {
        margin-top: 3px;
        color: var(--muted);
        font-size: 0.58rem;
      }

      .result-actions {
        display: flex;
        flex-wrap: wrap;
        justify-content: center;
        gap: 8px;
      }

      .loading-state,
      .error-state {
        display: grid;
        min-height: 55vh;
        place-items: center;
        text-align: center;
      }

      .loading-spinner {
        width: 46px;
        height: 46px;
        margin: 0 auto 12px;
        border: 5px solid #e6d9eb;
        border-top-color: var(--primary);
        border-radius: 50%;
        animation: spin 900ms linear infinite;
      }

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

      .error-state div {
        max-width: 520px;
        padding: 24px;
        border: 1px solid #e4c7c8;
        border-radius: 12px;
        background: var(--danger-soft);
      }

      @media (max-width: 800px) {
        .hero {
          grid-template-columns: 1fr;
        }

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

        .mode-card {
          display: grid;
          grid-template-columns: auto 1fr;
          column-gap: 13px;
        }

        .mode-card h3 {
          align-self: end;
          margin-top: 0;
        }

        .mode-card p,
        .mode-meta {
          grid-column: 2;
        }

        .mode-card p {
          min-height: 0;
        }

        .mastery-cell {
          border-radius: 2px;
        }
      }

      @media (max-width: 600px) {
        .topbar-inner,
        .app-shell {
          width: calc(100% - 24px);
        }

        .topbar-inner {
          min-height: 58px;
        }

        .brand-copy span,
        .top-stat:first-child {
          display: none;
        }

        .top-stat {
          min-width: 62px;
          padding-inline: 6px;
        }

        .app-shell {
          padding-top: 18px;
        }

        .hero-main {
          padding: 24px 20px;
        }

        .progress-card {
          padding: 18px;
        }

        .section-heading {
          display: block;
        }

        .difficulty-card {
          width: 100%;
          margin-top: 10px;
          overflow-x: auto;
        }

        .difficulty-button {
          flex: 1 0 auto;
        }

        .mode-card {
          padding: 16px;
        }

        .mastery-card {
          padding: 13px;
        }

        .mini-periodic-table {
          gap: 2px;
        }

        .game-toolbar {
          padding: 12px;
        }

        .game-toolbar-main {
          align-items: flex-start;
        }

        .game-identity-copy {
          display: none;
        }

        .live-stats {
          flex: 1;
          justify-content: flex-end;
        }

        .live-stat {
          min-width: 68px;
          padding-inline: 7px;
        }

        .question-card {
          margin-top: 12px;
          padding: 17px 14px;
        }

        .question-text {
          margin-top: 18px;
        }

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

        .answer-button {
          min-height: 52px;
        }

        .feedback {
          grid-template-columns: auto minmax(0, 1fr);
        }

        .earned-points {
          grid-column: 2;
        }

        .result-grid {
          gap: 5px;
        }

        .result-metric {
          padding-inline: 4px;
        }
      }

      @media (prefers-reduced-motion: reduce) {
        *,
        *::before,
        *::after {
          scroll-behavior: auto !important;
          animation-duration: 0.01ms !important;
          animation-iteration-count: 1 !important;
          transition-duration: 0.01ms !important;
        }
      }