/* Standardized Baseline Typography */
        html {
            font-size: 16px;
        }

        /* Shared kit mapping */
        :root {
            --kit-accent: #6366f1;
            --kit-accent-ink: #ffffff;
            --kit-accent-glow: rgba(99, 102, 241, 0.3);
            --kit-surface: #0f172a;
            --kit-border: #334155;
            --kit-input-bg: #1e293b;
            --kit-error: #ef4444;

            /* Rope-bridge scene tokens (dark, default) */
            --bridge-sky-top: #1e293b;
            --bridge-sky-bottom: #0f172a;
            --bridge-chasm: #020617;
            --bridge-rope: #b58a5c;
            --bridge-plank-bg: linear-gradient(180deg, #c99a63, #8a5a2b);
            --bridge-plank-border: #6b4423;
            --bridge-plank-text: #241407;
            --bridge-rack-bg: rgba(15, 23, 42, 0.6);
            --bridge-rack-border: #334155;
            --bridge-gap-border: #64748b;
            --bridge-gap-bg: rgba(2, 6, 23, 0.45);
            --bridge-hiker-shadow: rgba(0, 0, 0, 0.5);
            --bridge-rope-good: #f59e0b;
            --bridge-rope-lost: #475569;
            --bridge-toast-bg: #1e293b;
            --bridge-toast-text: #f8fafc;
            --bridge-toast-border: #334155;
        }

        body.light-mode {
            --kit-accent: #4338ca;
            --kit-accent-ink: #ffffff;
            --kit-accent-glow: rgba(67, 56, 202, 0.25);
            --kit-surface: #ffffff;
            --kit-border: #cbd5e1;
            --kit-input-bg: #f8fafc;
            --kit-error: #dc2626;

            /* Rope-bridge scene tokens (light override) */
            --bridge-sky-top: #bfdbfe;
            --bridge-sky-bottom: #e0f2fe;
            --bridge-chasm: #94a3b8;
            --bridge-rope: #92663f;
            --bridge-plank-bg: linear-gradient(180deg, #e0b479, #ad7a3d);
            --bridge-plank-border: #7a4a1e;
            --bridge-plank-text: #241407;
            --bridge-rack-bg: rgba(255, 255, 255, 0.75);
            --bridge-rack-border: #cbd5e1;
            --bridge-gap-border: #64748b;
            --bridge-gap-bg: rgba(148, 163, 184, 0.3);
            --bridge-hiker-shadow: rgba(0, 0, 0, 0.25);
            --bridge-rope-good: #d97706;
            --bridge-rope-lost: #cbd5e1;
            --bridge-toast-bg: #ffffff;
            --bridge-toast-text: #0f172a;
            --bridge-toast-border: #cbd5e1;
        }

        body {
            font-family: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
            background-color: #0f172a; /* Slate 900 */
            color: #f8fafc;
            transition: background-color 0.25s ease, color 0.25s ease;
        }

        .glow {
            box-shadow: 0 0 15px rgba(99, 102, 241, 0.3);
        }
        .glow-gold {
            box-shadow: 0 0 18px rgba(245, 158, 11, 0.4);
        }

        /* Math Fractions Styling */
        sup {
            font-size: 0.8em;
            font-weight: 800;
            vertical-align: super;
        }
        sub {
            font-size: 0.8em;
            font-weight: 800;
            vertical-align: sub;
        }

        /* PERMANENT DARK LOGO CARD */
        .logo-permanent-dark {
            background-color: #0f172a !important;
            border: 1px solid #334155 !important;
            box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, 0.4);
        }

        /* DARK MODE GRADIENTS & STYLES (DEFAULT) */
        .title-gradient {
            background: linear-gradient(135deg, #60a5fa 0%, #a5b4fc 50%, #c084fc 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }

        /* LIGHT MODE HIGH-CONTRAST OVERRIDES */
        body.light-mode {
            background-color: #f1f5f9; /* Slate 100 */
            color: #0f172a;
        }

        body.light-mode header {
            background-color: #ffffff;
            border-color: #cbd5e1;
            box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
        }

        body.light-mode .title-gradient {
            background: linear-gradient(135deg, #1e1b4b 0%, #3730a3 50%, #581c87 100%);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
        }

        body.light-mode .text-sub-theme {
            color: #475569 !important;
        }

        body.light-mode .score-box-theme {
            background-color: #ffffff !important;
            border-color: #cbd5e1 !important;
            box-shadow: 0 2px 6px rgba(0, 0, 0, 0.04);
        }
        body.light-mode #score {
            color: #d97706 !important;
        }
        body.light-mode #progress-text {
            color: #4338ca !important;
        }

        body.light-mode .tab-active {
            background-color: #e0e7ff !important;
            border-color: #4338ca !important;
            color: #1e1b4b !important;
            font-weight: 800;
        }
        body.light-mode .tab-inactive {
            background-color: #ffffff !important;
            border-color: #cbd5e1 !important;
            color: #334155 !important;
            opacity: 1 !important;
        }

        body.light-mode .game-card-theme {
            background-color: #ffffff !important;
            border-color: #cbd5e1 !important;
            box-shadow: 0 8px 20px -5px rgba(0, 0, 0, 0.05);
        }

        body.light-mode .badge-standard {
            background-color: #e0e7ff !important;
            color: #3730a3 !important;
            border-color: #a5b4fc !important;
        }
        body.light-mode .badge-challenge {
            background-color: #fef3c7 !important;
            color: #92400e !important;
            border-color: #fcd34d !important;
        }

        body.light-mode #question-text {
            color: #0f172a !important;
        }

        body.light-mode .opt-btn-theme {
            background-color: #f8fafc !important;
            border-color: #cbd5e1 !important;
            color: #0f172a !important;
        }
        body.light-mode .opt-btn-theme:hover {
            background-color: #e0e7ff !important;
            border-color: #4338ca !important;
        }
        body.light-mode .opt-badge-theme {
            background-color: #ffffff !important;
            border-color: #a5b4fc !important;
            color: #3730a3 !important;
        }

        body.light-mode .modal-inner-theme {
            background-color: #ffffff !important;
            border-color: #cbd5e1 !important;
        }
        body.light-mode .modal-box-theme {
            background-color: #f8fafc !important;
            border-color: #cbd5e1 !important;
            color: #1e293b !important;
        }

        /* ==========================================================
           Rope-Bridge Plank Builder — drag-and-drop mechanic
           ========================================================== */

        .lives-row {
            display: flex;
            gap: 4px;
            font-size: 1.15rem;
            line-height: 1;
        }
        .rope-icon {
            transition: opacity 0.3s ease, filter 0.3s ease, transform 0.3s ease;
        }
        .rope-icon.lost {
            opacity: 0.28;
            filter: grayscale(1);
            transform: scale(0.9) rotate(-8deg);
        }

        .bridge-scene {
            position: relative;
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 10px;
            min-height: 150px;
            padding: 18px 16px 14px;
            border-radius: 16px;
            background: linear-gradient(180deg, var(--bridge-sky-top), var(--bridge-sky-bottom));
            border: 1px solid var(--bridge-rack-border);
            overflow: hidden;
            transition: background 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
        }
        .bridge-scene.challenge-gap {
            box-shadow: 0 0 0 2px var(--bridge-rope-good) inset;
        }
        .bridge-scene.boss-gap {
            box-shadow: 0 0 0 2px var(--kit-error) inset;
        }

        /* Vertical cliff panel: flag at the top, current foothold gap below it,
           climber below that — the climber moves UP past the gap on every
           correct answer instead of a static sprite that never advances. */
        .cliff-face {
            position: relative;
            z-index: 1;
            width: 100%;
            max-width: 230px;
            height: 300px;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: flex-start;
            padding: 14px 0 10px;
            border-left: 3px dashed var(--bridge-rope);
            border-right: 3px dashed var(--bridge-rope);
            border-radius: 14px;
            background: linear-gradient(180deg, transparent 0%, var(--bridge-chasm) 115%);
        }

        .planks-crossed {
            position: relative;
            z-index: 2;
            display: flex;
            gap: 4px;
            align-items: center;
            justify-content: center;
            flex-wrap: wrap;
            padding-top: 2px;
        }
        .mini-plank {
            width: 14px;
            height: 9px;
            border-radius: 2px;
            background: var(--bridge-rack-border);
            opacity: 0.45;
            flex-shrink: 0;
        }
        .mini-plank.done {
            background: var(--bridge-plank-border);
            opacity: 1;
            box-shadow: 0 0 6px var(--bridge-rope-good);
        }

        .hiker-wrap {
            position: relative;
            z-index: 3;
            display: flex;
            flex-direction: column;
            align-items: center;
            flex-shrink: 0;
            transition: transform 0.6s cubic-bezier(.34,1.56,.64,1);
            transform: translate(0, 0) rotate(0deg);
        }
        .hiker {
            width: 46px;
            height: 60px;
            overflow: visible;
            color: var(--bridge-rope-good);
            filter: drop-shadow(0 4px 4px var(--bridge-hiker-shadow));
            animation: hikerIdleBob 1.8s ease-in-out infinite;
        }
        .hiker-head {
            fill: currentColor;
        }
        .hiker-torso,
        .hiker-arm-up,
        .hiker-arm-down,
        .hiker-leg-a,
        .hiker-leg-b {
            fill: none;
            stroke: currentColor;
            stroke-width: 6;
            stroke-linecap: round;
            stroke-linejoin: round;
        }
        @keyframes hikerIdleBob {
            0%, 100% { transform: translateY(0) rotate(0deg); }
            50%      { transform: translateY(-3px) rotate(-3deg); }
        }
        .hiker-quip {
            position: absolute;
            bottom: 100%;
            margin-bottom: 8px;
            left: 50%;
            transform: translate(-50%, 4px) scale(0.92);
            background: var(--bridge-toast-bg);
            color: var(--bridge-toast-text);
            border: 1px solid var(--bridge-toast-border);
            padding: 4px 10px;
            border-radius: 10px;
            font-size: 0.68rem;
            font-weight: 800;
            max-width: 230px;
            white-space: normal;
            text-align: center;
            opacity: 0;
            pointer-events: none;
            transition: opacity 0.2s ease, transform 0.2s ease;
            z-index: 5;
        }
        .hiker-quip.show {
            opacity: 1;
            transform: translate(-50%, 0) scale(1);
        }

        .gap-slot {
            position: relative;
            z-index: 2;
            flex-shrink: 0;
            width: 112px;
            height: 72px;
            /* Deliberate clearance below the gap so the hiker-quip bubble
               (which pops up above the climber) has room to appear without
               overlapping the gap-hint text above it. */
            margin-bottom: 64px;
            border: 3px dashed var(--bridge-gap-border);
            border-radius: 12px;
            background: var(--bridge-gap-bg);
            display: flex;
            align-items: center;
            justify-content: center;
            text-align: center;
            padding: 6px;
            transition: border-color 0.2s ease, background 0.2s ease;
        }
        .gap-slot.hover-target {
            border-color: var(--bridge-rope-good);
            background: rgba(245, 158, 11, 0.18);
        }
        .gap-slot.wobble {
            animation: gapWobble 0.45s ease;
            border-color: var(--kit-error);
        }
        @keyframes gapWobble {
            0%, 100% { transform: translateX(0) rotate(0deg); }
            20% { transform: translateX(-6px) rotate(-2deg); }
            40% { transform: translateX(6px) rotate(2deg); }
            60% { transform: translateX(-4px) rotate(-1deg); }
            80% { transform: translateX(4px) rotate(1deg); }
        }
        .gap-slot.filled {
            border-style: solid;
            border-color: var(--bridge-rope-good);
        }
        .gap-hint {
            font-size: 0.68rem;
            font-weight: 800;
            color: var(--kit-accent);
            opacity: 0.85;
            line-height: 1.2;
            transition: opacity 0.2s ease;
        }
        .challenge-gap .gap-slot,
        .boss-gap .gap-slot {
            width: 150px;
        }

        .finish-post {
            font-size: 1.6rem;
            opacity: 0.9;
            z-index: 2;
            flex-shrink: 0;
            margin-bottom: 16px;
        }

        .rack-label {
            font-size: 0.72rem;
            font-weight: 800;
            text-transform: uppercase;
            letter-spacing: 0.05em;
            color: var(--kit-accent);
            margin: 16px 0 8px;
            opacity: 0.9;
        }
        .plank-rack {
            display: flex;
            flex-wrap: wrap;
            gap: 12px;
            padding: 14px;
            border-radius: 14px;
            background: var(--bridge-rack-bg);
            border: 1px solid var(--bridge-rack-border);
        }
        .plank-slot {
            flex: 1 1 130px;
            min-width: 110px;
            max-width: 260px;
            height: 62px;
            position: relative;
        }
        .plank-tile {
            position: relative;
            width: 100%;
            height: 100%;
            display: flex;
            align-items: center;
            justify-content: center;
            text-align: center;
            padding: 8px 10px;
            box-sizing: border-box;
            border-radius: 10px;
            background: var(--bridge-plank-bg);
            border: 3px solid var(--bridge-plank-border);
            color: var(--bridge-plank-text);
            font-weight: 800;
            font-size: 0.92rem;
            line-height: 1.15;
            cursor: grab;
            touch-action: none;
            user-select: none;
            -webkit-user-select: none;
            box-shadow: 0 3px 0 var(--bridge-plank-border), 0 6px 10px rgba(0, 0, 0, 0.25);
        }
        .plank-tile:active {
            cursor: grabbing;
        }
        .plank-tile.dragging {
            box-shadow: 0 12px 20px rgba(0, 0, 0, 0.35);
            filter: brightness(1.06);
        }
        .plank-tile.disabled {
            pointer-events: none;
        }
        .plank-tile.tried-wrong {
            outline: 2px dashed var(--kit-error);
            outline-offset: 2px;
        }
        .plank-tile.crack {
            animation: plankCrack 0.4s ease;
        }
        @keyframes plankCrack {
            0%, 100% { transform: rotate(0deg); }
            25% { transform: rotate(-6deg); }
            50% { transform: rotate(5deg); }
            75% { transform: rotate(-3deg); }
        }
        .plank-tile.snap-correct {
            box-shadow: 0 0 0 3px var(--bridge-rope-good), 0 6px 14px rgba(0, 0, 0, 0.3);
        }

        #toast {
            position: fixed;
            left: 50%;
            bottom: 24px;
            transform: translate(-50%, 10px);
            background: var(--bridge-toast-bg);
            color: var(--bridge-toast-text);
            border: 1px solid var(--bridge-toast-border);
            padding: 10px 18px;
            border-radius: 12px;
            font-weight: 800;
            font-size: 0.85rem;
            box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
            opacity: 0;
            pointer-events: none;
            transition: opacity 0.2s ease, transform 0.2s ease;
            z-index: 80;
            max-width: 90vw;
            text-align: center;
        }
        #toast.show {
            opacity: 1;
            transform: translate(-50%, 0);
        }

        @media (max-width: 480px) {
            .bridge-scene {
                gap: 6px;
                padding: 12px 10px 16px;
            }
            .cliff-face {
                height: 260px;
                max-width: 190px;
            }
            .planks-crossed {
                display: none;
            }
            .gap-slot {
                width: 92px;
                height: 64px;
                margin-bottom: 54px;
            }
            .challenge-gap .gap-slot,
            .boss-gap .gap-slot {
                width: 120px;
            }
            .plank-slot {
                flex: 1 1 100%;
                height: 56px;
            }
        }