:root {
            --lesson-bg: #f5f1e8;
            --lesson-surface: rgba(255,255,255,0.82);
            --lesson-border: rgba(38, 67, 57, 0.12);
            --lesson-ink: #17362f;
            --lesson-muted: #65736d;
            --lesson-accent: #235a53;
            --lesson-accent-strong: #173f39;
            --lesson-warm: #a06c22;
            --lesson-shadow: 0 24px 44px rgba(24, 35, 30, 0.08);
        }

        * { box-sizing: border-box; }

        body.lesson-scene-page {
            margin: 0;
            padding: 20px;
            min-height: 100vh;
            background:
                radial-gradient(circle at top left, rgba(64, 106, 95, 0.08), transparent 26%),
                linear-gradient(180deg, #f7f4ec 0%, var(--lesson-bg) 100%);
            color: var(--lesson-ink);
            font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
        }

        .lesson-shell {
            min-height: 100vh;
            min-height: 100vh;
            display: grid;
            grid-template-columns: 288px minmax(0, 1fr);
            max-width: 1460px;
            margin: 0 auto;
            border: 1px solid rgba(25, 54, 46, 0.08);
            border-radius: 30px;
            overflow: hidden;
            box-shadow: 0 30px 60px rgba(24, 35, 30, 0.08);
        }

        .lesson-sidebar {
            position: sticky;
            top: 0;
            height: 100vh;
            padding: 18px 14px 18px;
            border-right: 1px solid rgba(25, 54, 46, 0.08);
            background: transparent;
            overflow: hidden;
            display: flex;
            flex-direction: column;
            gap: 14px;
        }

        .lesson-side-panel {
            background: rgba(255,255,255,0.72);
            border: 1px solid rgba(25, 54, 46, 0.08);
            border-radius: 30px;
            box-shadow: 0 24px 44px rgba(24, 35, 30, 0.06);
            padding: 20px 16px;
            display: flex;
            flex: 1 1 auto;
            min-height: 0;
            flex-direction: column;
            overflow: hidden;
        }

        .lesson-side-title {
            margin: 0 10px 14px;
            color: #8a6d3b;
            font-size: 0.9rem;
            font-weight: 700;
            letter-spacing: 0.04em;
        }

        .lesson-nav {
            display: grid;
            gap: 8px;
            min-height: 0;
            overflow-y: auto;
            padding-right: 6px;
            scrollbar-width: thin;
            scrollbar-color: rgba(35, 90, 83, 0.28) transparent;
        }

        .lesson-nav::-webkit-scrollbar {
            width: 8px;
        }

        .lesson-nav::-webkit-scrollbar-thumb {
            background: rgba(35, 90, 83, 0.22);
            border-radius: 999px;
        }

        .lesson-nav::-webkit-scrollbar-track {
            background: transparent;
        }

        .lesson-nav-link {
            display: block;
            padding: 14px 16px;
            border-radius: 22px;
            color: var(--lesson-ink);
            text-decoration: none;
            transition: transform 0.18s ease, background 0.18s ease;
        }

        .lesson-nav-link:hover {
            transform: translateY(-1px);
            background: rgba(255,255,255,0.42);
        }

        .lesson-nav-link.is-active {
            background: #edf4ec;
            box-shadow: inset 0 0 0 1px rgba(75, 126, 94, 0.22);
        }

        .lesson-nav-link strong,
        .lesson-nav-link span {
            display: inline;
            line-height: 1.45;
        }

        .lesson-nav-link strong {
            font-size: 0.98rem;
            font-weight: 700;
        }

        .lesson-nav-link span {
            font-size: 0.98rem;
            font-weight: 700;
        }

        .lesson-nav-link small {
            display: block;
            margin-top: 8px;
            color: rgba(23, 54, 47, 0.56);
            font-size: 0.84rem;
            font-weight: 700;
        }

        .lesson-side-dock {
            flex: 0 0 auto;
            padding: 0 2px;
        }

        .lesson-dock-btn {
            display: block;
            width: 100%;
            border: 0;
            border-radius: 999px;
            padding: 18px 18px;
            background: linear-gradient(135deg, #0f3d30 0%, #123f33 100%);
            color: #fff;
            font-weight: 800;
            font-size: 0.95rem;
            text-align: center;
            text-decoration: none;
            box-shadow: 0 16px 26px rgba(15, 61, 48, 0.18);
        }

        .lesson-main {
            min-width: 0;
            padding: 24px 28px 64px;
        }

        .lesson-topbar {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 16px;
            margin-bottom: 18px;
        }

        .lesson-topbar-nav {
            display: flex;
            align-items: center;
            gap: 12px;
            flex-wrap: wrap;
        }

        .lesson-topbar-nav a {
            color: var(--lesson-muted);
            text-decoration: none;
            font-size: 1rem;
            font-weight: 700;
            letter-spacing: 0.02em;
            padding: 8px 12px;
            border-radius: 999px;
            transition: color 0.18s ease, background 0.18s ease, transform 0.18s ease;
        }

        .lesson-topbar-nav a:hover {
            color: var(--lesson-accent-strong);
            background: rgba(35, 90, 83, 0.08);
            transform: translateY(-1px);
        }

        .lesson-topbar-note {
            color: var(--lesson-muted);
            text-decoration: none;
            font-size: 0.92rem;
        }

        .lesson-topbar-nav a.is-active {
            color: var(--lesson-accent-strong);
            font-weight: 900;
            background: rgba(35, 90, 83, 0.1);
            box-shadow: inset 0 -2px 0 rgba(35, 90, 83, 0.9);
        }

        .lesson-topbar-nav a[href$="path.html"],
        .lesson-topbar-nav a[href$="a2/index.html"] {
            font-size: 1.08rem;
            letter-spacing: 0.04em;
        }

        .lesson-hero {
            position: relative;
            overflow: hidden;
            border-radius: 28px;
            min-height: 336px;
            padding: 50px 52px;
            margin-bottom: 18px;
            background: linear-gradient(135deg, #235a53 0%, #214744 58%, #1c3835 100%);
            color: #fff;
            box-shadow: 0 28px 48px rgba(20, 35, 31, 0.16);
        }

        .lesson-hero::before {
            content: "";
            position: absolute;
            right: -40px;
            bottom: -60px;
            width: 260px;
            height: 260px;
            border-radius: 36px;
            background: radial-gradient(circle, rgba(255,255,255,0.1), transparent 64%);
            transform: rotate(14deg);
        }

        .lesson-hero::after {
            content: "\2726";
            position: absolute;
            right: 42px;
            bottom: 28px;
            font-size: 5.6rem;
            color: rgba(255,255,255,0.1);
            line-height: 1;
        }

        .lesson-hero-inner {
            position: relative;
            z-index: 1;
            max-width: 720px;
        }

        .lesson-kicker {
            display: inline-flex;
            align-items: center;
            gap: 10px;
            margin-bottom: 14px;
            padding: 6px 14px;
            border-radius: 999px;
            background: rgba(255,255,255,0.12);
            font-size: 0.78rem;
            font-weight: 800;
            letter-spacing: 0.14em;
            text-transform: uppercase;
        }

        .lesson-hero h1 {
            margin: 0 0 10px;
            font-size: clamp(2.8rem, 5vw, 4.5rem);
            line-height: 1;
            letter-spacing: -0.05em;
        }

        .lesson-hero p {
            margin: 0;
            max-width: 680px;
            line-height: 1.9;
            color: rgba(255,255,255,0.88);
            font-size: 1.08rem;
        }

        .lesson-hero-actions {
            display: flex;
            align-items: center;
            gap: 12px;
            flex-wrap: wrap;
            margin-top: 28px;
        }

        .hero-btn,
        .hero-btn-outline,
        .scene-play-btn,
        .trans-btn {
            border-radius: 999px;
            cursor: pointer;
            font-weight: 700;
        }

        .hero-btn {
            border: 0;
            display: inline-flex;
            align-items: center;
            gap: 10px;
            padding: 16px 26px;
            font-size: 1.08rem;
            font-weight: 800;
            background: linear-gradient(135deg, #ffffff 0%, #f1f7f4 100%);
            color: var(--lesson-accent-strong);
            box-shadow: 0 10px 20px rgba(15, 61, 48, 0.2);
            transition: transform 0.18s ease, box-shadow 0.18s ease;
        }

        .hero-btn::before {
            content: "\25B6";
            font-size: 0.84rem;
            line-height: 1;
        }

        .hero-btn:hover {
            transform: translateY(-1px);
            box-shadow: 0 14px 24px rgba(15, 61, 48, 0.24);
        }

        .scene-play-btn {
            display: inline-flex;
            align-items: center;
            gap: 8px;
        }

        .scene-play-btn::before {
            content: "\25B6";
            font-size: 0.72rem;
            line-height: 1;
        }

        .scene-play-btn--primary {
            border: 0;
            background: linear-gradient(135deg, #0f3d30 0%, #184a3d 100%);
            color: #fff;
            font-weight: 800;
            padding: 12px 20px;
            box-shadow: 0 10px 20px rgba(15, 61, 48, 0.2);
        }

        .scene-play-btn--primary::before {
            content: "";
        }

        .scene-play-btn--primary:hover {
            background: linear-gradient(135deg, #0c3228 0%, #123f33 100%);
            box-shadow: 0 14px 24px rgba(15, 61, 48, 0.24);
        }

        .hero-btn-outline,
        .scene-play-btn,
        .trans-btn {
            border: 1px solid rgba(35, 90, 83, 0.16);
            background: rgba(255,255,255,0.72);
            color: var(--lesson-ink);
            padding: 11px 17px;
        }

        .hero-btn-outline:hover,
        .scene-play-btn:hover,
        .trans-btn:hover,
        .trans-btn.active {
            border-color: rgba(35, 90, 83, 0.4);
            background: rgba(35, 90, 83, 0.08);
        }

        .lesson-scene-tabs {
            display: flex;
            gap: 12px;
            flex-wrap: wrap;
            margin: 0 0 26px;
        }

        .lesson-scene-btn {
            border: 1px solid rgba(35, 90, 83, 0.16);
            border-radius: 18px;
            background: rgba(255,255,255,0.88);
            color: var(--lesson-ink);
            padding: 14px 16px;
            min-width: 176px;
            text-align: left;
            cursor: pointer;
            box-shadow: 0 10px 18px rgba(24, 35, 30, 0.05);
            transition: transform 0.18s ease, border-color 0.18s ease, background 0.18s ease, box-shadow 0.18s ease;
        }

        .lesson-scene-btn:hover {
            transform: translateY(-1px);
            border-color: rgba(35, 90, 83, 0.28);
            box-shadow: 0 14px 24px rgba(24, 35, 30, 0.08);
        }

        .lesson-scene-btn.is-active {
            background: linear-gradient(135deg, #235a53 0%, #184841 100%);
            border-color: rgba(24, 72, 65, 0.95);
            color: #fff;
            box-shadow: 0 18px 30px rgba(25, 72, 65, 0.18);
            transform: translateY(-2px);
        }

        .lesson-scene-btn strong {
            display: block;
            margin-bottom: 6px;
            font-size: 0.95rem;
        }

        .lesson-scene-btn span {
            color: var(--lesson-muted);
            font-size: 0.82rem;
            font-weight: 700;
        }

        .lesson-scene-btn.is-active span {
            color: rgba(255,255,255,0.86);
        }

        .lesson-section {
            margin-bottom: 34px;
        }

        .lesson-section-head {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 16px;
            margin-bottom: 14px;
        }

        .lesson-section-head h2 {
            margin: 0;
            font-size: 1.5rem;
            letter-spacing: -0.03em;
        }

        .lesson-section-head span {
            color: var(--lesson-muted);
            font-size: 0.9rem;
        }

        .lesson-dialogue-wrap {
            background: rgba(255,255,255,0.62);
            border: 1px solid rgba(35, 90, 83, 0.08);
            border-radius: 26px;
            padding: 20px;
        }

        .lesson-dialogue-tools {
            display: flex;
            gap: 10px;
            flex-wrap: wrap;
            margin-bottom: 18px;
        }

        .lesson-dialogue-tools .scene-play-btn--cta {
            border: 0;
            padding: 12px 20px;
            font-size: 1rem;
            font-weight: 900;
            letter-spacing: 0.01em;
            background: linear-gradient(135deg, #0f3d30 0%, #1f5e4e 100%);
            color: #ffffff;
            box-shadow: 0 10px 20px rgba(15, 61, 48, 0.28), 0 0 0 4px rgba(31, 94, 78, 0.16);
            animation: dialogue-cta-pulse 1.8s ease-in-out infinite;
        }

        .lesson-dialogue-tools .scene-play-btn--cta::before {
            content: "\25B6";
            font-size: 0.78rem;
            line-height: 1;
        }

        .lesson-dialogue-tools .scene-play-btn--cta:hover {
            background: linear-gradient(135deg, #0c3228 0%, #174c3f 100%);
            transform: translateY(-1px);
            box-shadow: 0 14px 24px rgba(15, 61, 48, 0.32), 0 0 0 4px rgba(31, 94, 78, 0.2);
        }

        .lesson-dialogue-tools .scene-play-btn--cta.is-playing {
            background: linear-gradient(135deg, #396b5f 0%, #4f8578 100%);
            cursor: not-allowed;
            opacity: 0.92;
            animation: none;
        }

        @keyframes dialogue-cta-pulse {
            0% {
                box-shadow: 0 10px 20px rgba(15, 61, 48, 0.28), 0 0 0 0 rgba(31, 94, 78, 0.28);
            }
            70% {
                box-shadow: 0 10px 20px rgba(15, 61, 48, 0.3), 0 0 0 10px rgba(31, 94, 78, 0);
            }
            100% {
                box-shadow: 0 10px 20px rgba(15, 61, 48, 0.28), 0 0 0 0 rgba(31, 94, 78, 0);
            }
        }

        .lesson-dialogue {
            display: grid;
            gap: 18px;
        }

        .dialogue-row {
            display: flex;
            align-items: flex-end;
            gap: 12px;
        }

        .dialogue-row.playing {
            background: rgba(35, 90, 83, 0.08);
            border-radius: 12px;
            padding: 8px 12px;
            margin: 4px 0;
        }

        .dialogue-row.is-right {
            justify-content: flex-end;
        }

        .dialogue-meta {
            display: inline-flex;
            align-items: center;
            gap: 8px;
            width: auto;
            min-width: 0;
            flex: 0 0 auto;
            text-align: left;
            white-space: nowrap;
        }

        .dialogue-avatar {
            width: 42px;
            height: 42px;
            border-radius: 50%;
            display: grid;
            place-items: center;
            font-weight: 800;
            color: #fff;
            background: linear-gradient(135deg, #244e47 0%, #1a3531 100%);
            box-shadow: inset 0 0 0 2px rgba(255,255,255,0.18);
        }

        .dialogue-avatar--warm {
            background: linear-gradient(135deg, #a64943 0%, #7e2f2f 100%);
        }

        .dialogue-meta span {
            display: inline-block;
            margin-top: 0;
            color: var(--lesson-muted);
            font-size: 0.82rem;
            line-height: 1;
        }

        .dialogue-bubble {
            max-width: min(560px, 78%);
            background: rgba(255,255,255,0.92);
            border: 1px solid rgba(23, 63, 57, 0.1);
            border-radius: 22px;
            padding: 16px 18px;
            box-shadow: 0 16px 28px rgba(24, 35, 30, 0.06);
        }

        .dialogue-row.is-left .dialogue-bubble { border-top-left-radius: 8px; }
        .dialogue-row.is-right .dialogue-bubble { border-top-right-radius: 8px; }

        .dialogue-line {
            margin: 0;
            font-size: 1.04rem;
            line-height: 1.6;
            color: var(--lesson-accent-strong);
        }

        .dialogue-line button {
            margin-left: 8px;
            width: 32px;
            height: 32px;
            border: 0;
            border-radius: 999px;
            background: #e3efe5;
            color: #285138;
            cursor: pointer;
            font-size: 0.9rem;
            vertical-align: middle;
        }

        .dialogue-trans {
            display: none;
            margin-top: 8px;
            color: var(--lesson-muted);
            font-size: 0.9rem;
            line-height: 1.7;
        }

        .dialogue-trans.show {
            display: block;
        }

        .lesson-grid {
            display: grid;
            grid-template-columns: repeat(2, minmax(0, 1fr));
            gap: 16px;
        }

        .lesson-card {
            background: var(--lesson-surface);
            border: 1px solid var(--lesson-border);
            border-radius: 22px;
            padding: 18px;
            box-shadow: var(--lesson-shadow);
        }

        .lesson-card h3 {
            margin: 0 0 10px;
            font-size: 1.02rem;
        }

        .lesson-card p {
            margin: 0 0 12px;
            color: var(--lesson-muted);
            line-height: 1.75;
            font-size: 0.92rem;
        }

        .lesson-mini-list {
            display: grid;
            gap: 8px;
        }

        .lesson-mini-row {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 14px;
            padding: 10px 12px;
            border-radius: 14px;
            background: rgba(255,255,255,0.72);
            font-size: 0.9rem;
        }

        .lesson-mini-row strong { font-weight: 700; }

        .lesson-vocab-grid {
            display: grid;
            grid-template-columns: repeat(4, minmax(0, 1fr));
            gap: 14px;
        }

        .lesson-vocab-card {
            background: rgba(255,255,255,0.9);
            border: 1px solid rgba(23, 63, 57, 0.08);
            border-radius: 18px;
            padding: 16px 14px;
        }

        .lesson-vocab-head {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 10px;
            margin-bottom: 6px;
        }

        .lesson-vocab-card strong {
            font-size: 1rem;
        }

        .lesson-vocab-head .play-btn {
            margin-left: auto;
            flex: 0 0 auto;
        }

        .lesson-vocab-card b {
            display: block;
            margin-bottom: 8px;
            color: var(--lesson-warm);
            font-size: 0.72rem;
            letter-spacing: 0.08em;
            text-transform: uppercase;
        }

        .lesson-vocab-card span {
            color: var(--lesson-muted);
            font-size: 0.88rem;
        }

        .lesson-exercise {
            padding: 22px;
            background: rgba(111, 94, 64, 0.08);
            border: 1px solid rgba(112, 94, 61, 0.12);
            border-radius: 26px;
        }

        .lesson-exercise h3 {
            margin: 0 0 16px;
            font-size: 1.2rem;
        }

        .lesson-exercise-list {
            display: grid;
            gap: 12px;
            margin-bottom: 18px;
        }

        .lesson-exercise-item {
            display: flex;
            align-items: flex-start;
            justify-content: space-between;
            gap: 12px;
            padding: 14px 16px;
            border-radius: 16px;
            background: rgba(255,255,255,0.74);
            border: 1px solid rgba(23, 63, 57, 0.08);
            line-height: 1.7;
        }

        .lesson-exercise-copy {
            flex: 1 1 auto;
            min-width: 0;
        }

        .lesson-exercise-item .play-btn {
            flex: 0 0 auto;
            margin-top: 2px;
        }

        .lesson-empty {
            padding: 18px 20px;
            border-radius: 18px;
            background: rgba(255,255,255,0.7);
            color: var(--lesson-muted);
            line-height: 1.7;
        }

        .lesson-footer {
            display: flex;
            justify-content: space-between;
            gap: 14px;
            flex-wrap: wrap;
            margin-top: 20px;
        }

        .lesson-footer a {
            text-decoration: none;
        }

        .lesson-footer-btn {
            border: 1px solid rgba(35, 90, 83, 0.16);
            border-radius: 999px;
            padding: 12px 18px;
            background: rgba(255,255,255,0.72);
            color: var(--lesson-ink);
            cursor: pointer;
            font-weight: 700;
        }

        .lesson-footer-btn.primary {
            background: linear-gradient(135deg, var(--lesson-accent-strong) 0%, var(--lesson-accent) 100%);
            color: #fff;
            border-color: transparent;
        }

        @media (max-width: 1180px) {
            .lesson-shell {
            min-height: 100vh; grid-template-columns: 1fr; }
            .lesson-sidebar {
                position: static;
                height: auto;
                border-right: 0;
                border-bottom: 1px solid rgba(25, 54, 46, 0.08);
            }
        }

        @media (max-width: 920px) {
            body.lesson-scene-page { padding: 12px; }
            .lesson-main { padding: 18px 16px 54px; }
            .lesson-hero { min-height: 280px; padding: 32px 24px; }
            .lesson-hero h1 { font-size: clamp(2.2rem, 8vw, 3rem); }
            .lesson-hero p { font-size: 1rem; }
            .lesson-grid, .lesson-vocab-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
        }

        @media (max-width: 640px) {
            body.lesson-scene-page { padding: 0; }
            .lesson-shell {
                min-height: 100vh;
                grid-template-columns: 1fr;
                border-radius: 0;
                border-left: 0;
                border-right: 0;
            }
            .lesson-sidebar {
                display: none;
            }
            .lesson-topbar {
                position: sticky;
                top: 0;
                z-index: 999;
                background: var(--lesson-surface);
                border-bottom: 1px solid var(--lesson-border);
                padding: 12px 16px;
                margin: 0 -16px 16px -16px;
                width: calc(100% + 32px);
            }
            .lesson-topbar-nav {
                flex-direction: row;
                gap: 8px;
                align-items: center;
            }
            .lesson-topbar-nav a {
                font-size: 0.875rem;
                padding: 6px 10px;
            }
            .lesson-topbar, .lesson-section-head, .lesson-hero-actions, .lesson-footer {
                flex-direction: column;
                align-items: flex-start;
            }
            .lesson-footer {
                position: fixed;
                bottom: 0;
                left: 0;
                right: 0;
                background: var(--lesson-surface);
                border-top: 1px solid var(--lesson-border);
                padding: 12px 16px;
                gap: 10px;
                z-index: 100;
            }
            .lesson-footer a {
                flex: 1;
                min-width: 0;
            }
            .lesson-scene-btn, .hero-btn, .hero-btn-outline, .scene-play-btn, .trans-btn {
                width: 100%;
            }
            .lesson-footer-btn {
                width: 100%;
                padding: 14px 16px;
                font-size: 0.95rem;
            }
            .dialogue-row, .dialogue-row.is-right {
                justify-content: flex-start;
            }
            .dialogue-bubble { max-width: 100%; }
            .lesson-grid, .lesson-vocab-grid { grid-template-columns: 1fr; }
            .lesson-main {
                padding: 0 16px 80px 16px;
            }
        }