body { font-family: 'Inter', sans-serif; background-color: #111827; color: #d1d5db; }
        #text-stream { font-family: 'Fira Code', monospace; transition: transform 0.15s linear; }
        .char { 
            display: inline-flex; 
            align-items: center; 
            justify-content: center; 
            width: 2rem; 
            height: 4rem; 
            text-align: center;
            transition: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
            border-radius: 6px;
            position: relative;
        }
        
        /* 普通字符美学优化 */
        .char.normal {
            color: #9ca3af;
            background: rgba(55, 65, 81, 0.1);
            border: 1px solid transparent;
        }
        
        /* 普通字符悬停效果 */
        .char.normal:hover {
            background: rgba(55, 65, 81, 0.2);
            transform: translateY(-1px);
        }
        
        /* 当前字符通用样式优化 */
        .char.current:not([data-char="space"]) {
            background: transparent;
            border-color: transparent;
            color: inherit;
            transform: none;
            box-shadow: none;
        }
        
        /* 已完成字符样式 */
        .char.completed.correct:not([data-char="space"]):not([data-char="enter"]) {
            background: linear-gradient(135deg, rgba(34, 197, 94, 0.1) 0%, rgba(22, 163, 74, 0.2) 100%);
            border: 1px solid rgba(34, 197, 94, 0.2);
            color: #22c55e;
        }
        
        /* 错误字符样式 */
        .char.completed.error:not([data-char="space"]):not([data-char="enter"]) {
            background: linear-gradient(135deg, rgba(239, 68, 68, 0.15) 0%, rgba(220, 38, 38, 0.25) 100%);
            border: 1px solid rgba(239, 68, 68, 0.3);
            color: #ef4444;
            animation: subtle-shake 0.4s ease-in-out;
        }
        
        /* 空格字符 - 极简优雅设计 */
        .char[data-char="space"] {
            background: rgba(148, 163, 184, 0.08);
            border: none;
            border-radius: 6px;
            min-width: 1.4rem;
            margin: 0 2px;
            position: relative;
            transition: all 0.2s ease;
            box-shadow: none;
        }
        
        /* 空格底部简洁指示线 */
        .char[data-char="space"]::after {
            content: '';
            position: absolute;
            bottom: 6px;
            left: 50%;
            transform: translateX(-50%);
            width: 80%;
            height: 1px;
            background: rgba(148, 163, 184, 0.4);
            border-radius: 0.5px;
        }
        
        /* 空格悬停 - 微妙提升 */
        .char[data-char="space"]:hover {
            background: rgba(148, 163, 184, 0.12);
            transform: translateY(-1px);
        }
        
        .char[data-char="space"]:hover::after {
            background: rgba(34, 211, 238, 0.6);
            width: 90%;
        }
        
        /* 当前空格 - 清新高亮 */
        .char[data-char="space"].current {
            background: rgba(34, 211, 238, 0.1) !important;
            border: 1px solid rgba(34, 211, 238, 0.3);
            transform: translateY(-1px);
            box-shadow: 0 0 0 2px rgba(34, 211, 238, 0.1);
        }
        
        .char[data-char="space"].current::after {
            background: #22d3ee;
            width: 90%;
            height: 2px;
            bottom: 4px;
        }
        
        /* 已完成空格 - 成功状态 */
        .char[data-char="space"].completed {
            background: rgba(34, 197, 94, 0.08);
            border: 1px solid rgba(34, 197, 94, 0.2);
        }
        
        .char[data-char="space"].completed::after {
            background: rgba(34, 197, 94, 0.6);
            width: 90%;
        }
        
        /* 错误空格 - 错误状态 */
        .char[data-char="space"].error {
            background: rgba(239, 68, 68, 0.1);
            border: 1px solid rgba(239, 68, 68, 0.3);
            animation: gentle-shake 0.3s ease-in-out;
        }
        
        .char[data-char="space"].error::after {
            background: rgba(239, 68, 68, 0.8);
            width: 90%;
        }
        
        /* 温和的错误动画 */
        @keyframes gentle-shake {
            0%, 100% { transform: translateX(0); }
            50% { transform: translateX(-1px); }
        }
        
        /* 错误脉动 */
        @keyframes error-pulse {
            0%, 100% { opacity: 0.8; }
            50% { opacity: 1; }
        }
        
        /* 脉动线条动画 */
        @keyframes pulse-line {
            0%, 100% { 
                opacity: 0.8; 
                transform: translateX(-50%) scale(1);
            }
            50% { 
                opacity: 1; 
                transform: translateX(-50%) scale(1.1);
            }
        }
        @keyframes shake { 0%, 100% { transform: translateX(0); } 10%, 30%, 50%, 70%, 90% { transform: translateX(-3px); } 20%, 40%, 60%, 80% { transform: translateX(3px); } }
        .shake { animation: shake 0.3s ease-in-out; }
        .key { transition: all 0.1s ease-out; border-bottom-width: 4px; }
        .key-active { transform: translateY(2px); border-bottom-width: 2px; filter: brightness(1.2); }
        .key-highlight { background-color: #374151 !important; color: #f3f4f6 !important; box-shadow: inset 0 0 0 2px #9ca3af; }
        .btn-base { transition: all 0.3s ease; }
        .btn-base:hover { transform: translateY(-4px); box-shadow: 0 10px 20px rgba(34, 211, 238, 0.2); }
        .particle { position: fixed; background: #22d3ee; border-radius: 50%; pointer-events: none; animation: fly-out 0.6s ease-out forwards; }
        @keyframes fly-out { 0% { transform: translate(0, 0) scale(1); opacity: 1; } 100% { transform: translate(var(--x), var(--y)) scale(0); opacity: 0; } }
        #focus-cursor { position: absolute; width: 2rem; height: 3px; background-color: #22d3ee; border-radius: 1.5px; top: 50%; left: 50%; transform: translate(-50%, 2.1rem); box-shadow: 0 0 10px #22d3ee; animation: pulse-cursor 1.5s infinite ease-in-out; }
        @keyframes pulse-cursor { 0%, 100% { opacity: 1; } 50% { opacity: 0.7; } }
        .finger { transition: fill 0.2s ease-in-out, stroke 0.2s ease-in-out; fill: #374151; stroke: #4b5563; stroke-width: 2; }
        .finger-highlight { fill: #22d3ee; stroke: #67e8f9; }
        .finger-cue { width: min(700px, calc(100% - 32px)); margin: 14px auto 0; padding: 14px 18px; display: flex; align-items: center; gap: 14px; border: 1px solid #374151; border-radius: 14px; background: #1f2937; color: #9ca3af; box-shadow: 0 8px 20px rgba(0,0,0,.16); }
        .finger-cue-kicker { color: #6b7280; font-size: 11px; letter-spacing: .08em; }
        .finger-cue strong { min-width: 38px; height: 38px; display: grid; place-items: center; border-radius: 9px; background: #22d3ee; color: #111827; font-size: 19px; font-family: 'Fira Code', monospace; }
        .finger-cue-label { color: #f3f4f6; font-weight: 700; font-size: 14px; }
        .finger-lane { display: flex; align-items: end; gap: 5px; height: 48px; margin-left: 4px; padding: 0 2px; }
        .finger-lane i { display: block; width: 13px; height: 30px; border-radius: 8px 8px 4px 4px; background: #4b5563; opacity: .82; transition: height .18s ease, background .18s ease, box-shadow .18s ease, transform .18s ease; }
        .finger-lane i:nth-child(4), .finger-lane i:nth-child(7) { height: 39px; }
        .finger-lane i:nth-child(5), .finger-lane i:nth-child(6) { height: 22px; }
        .finger-lane i:nth-child(6) { margin-left: 13px; }
        .finger-lane i.active { height: 46px; background: #22d3ee; opacity: 1; transform: translateY(-2px); box-shadow: 0 0 0 3px rgba(34,211,238,.16), 0 0 14px rgba(34,211,238,.6); }
        .finger-cue-help { margin-left: auto; color: #6b7280; font-size: 11px; }
        @media (max-width: 620px) { .finger-cue { gap: 8px; padding: 12px; } .finger-cue-help { display: none; } .finger-cue-label { font-size: 12px; } .finger-lane { margin-left: auto; gap: 4px; transform: scale(.88); transform-origin: right center; } }
        /* 空格是排版间距，不是一个可见的方框按键。 */
        .char[data-char="space"] { min-width: .55em !important; width: .55em; margin: 0 .08em; padding: 0; background: transparent !important; border: 0 !important; box-shadow: none !important; border-radius: 0; }
        .char[data-char="space"]::after { display: none; }
        .char[data-char="space"].current { background: transparent !important; border: 0 !important; box-shadow: none !important; transform: none; }
        .char[data-char="space"].current::after { display: block; bottom: -3px; left: 0; width: 100%; height: 2px; transform: none; background: #22d3ee; }
        .char[data-char="space"].completed { background: transparent !important; border: 0 !important; }
        .char[data-char="space"].completed::after { display: none; }
        #text-stream-container { display: flex; align-items: center; justify-content: center; }
        #text-stream { left: 0; top: 0; width: max-content; height: auto; min-height: 100%; display: flex; flex-wrap: nowrap; align-items: center; justify-content: flex-start; white-space: pre; }
        /* 文章模式：编辑部阅读稿——窄测量宽度、行级聚焦、换行时平滑上移。 */
        #typing-area:has(#text-stream-container.multi-line) {
            flex: 1 1 auto;
            height: auto;
            min-height: clamp(190px, 24vh, 240px);
            align-self: stretch;
        }
        #text-stream-container.multi-line {
            top: 50%;
            left: 50%;
            height: auto;
            width: min(calc(100% - 48px), 1120px);
            transform: translate(-50%, -50%);
            align-items: flex-start;
            justify-content: flex-start;
            overflow-x: hidden;
            overflow-y: auto;
            scroll-behavior: smooth;
            border: 1px solid rgba(148, 163, 184, .18);
            border-radius: 18px;
            background: rgba(15, 23, 42, .72);
            box-shadow: 0 18px 44px rgba(2, 6, 23, .22), inset 0 1px 0 rgba(255, 255, 255, .04);
            scrollbar-color: #475569 transparent;
            scrollbar-width: thin;
        }
        #text-stream.multi-line {
            display: block;
            width: 100%;
            max-width: 100%;
            min-height: auto;
            padding: 0 clamp(24px, 5vw, 56px);
            box-sizing: border-box;
            white-space: pre-wrap;
            line-height: 1.48;
            font-size: clamp(2.5rem, 3vw, 2.75rem);
            letter-spacing: .012em;
            color: #cbd5e1;
            word-break: normal;
            overflow-wrap: normal;
        }
        #text-stream.multi-line .char {
            display: inline;
            flex: initial;
            width: auto;
            min-width: 0;
            height: auto;
            line-height: inherit;
            margin: 0;
            vertical-align: baseline;
            opacity: .42;
            transition: color 220ms cubic-bezier(.25, 1, .5, 1), opacity 220ms cubic-bezier(.25, 1, .5, 1), text-shadow 220ms cubic-bezier(.25, 1, .5, 1);
        }
        #text-stream.multi-line .char.line-current,
        #text-stream.multi-line .char.current { opacity: 1; }
        #text-stream.multi-line .char.current { color: #f8fafc !important; text-shadow: 0 0 16px rgba(226, 232, 240, .14); }
        #text-stream.multi-line .char.completed.correct:not([data-char="space"]):not([data-char="enter"]) {
            background: transparent !important;
            border: 0 !important;
            box-shadow: none !important;
            color: #8fb3a2 !important;
        }
        #text-stream.multi-line .char.completed.error:not([data-char="space"]):not([data-char="enter"]) {
            background: transparent !important;
            border: 0 !important;
            box-shadow: none !important;
            color: #e5a4a4 !important;
        }
        #text-stream.multi-line .char[data-char="space"] { display: inline; width: auto; min-width: 0; margin: 0; white-space: normal; }
        #text-stream .char[data-char="enter"] { background: transparent !important; border: 0 !important; box-shadow: none !important; color: #64748b !important; }
        #text-stream .char[data-char="virtual-enter"] { flex-basis: 1.25rem; width: 1.25rem; height: auto; margin-left: .15rem; background: transparent !important; border: 0 !important; box-shadow: none !important; color: #a8b4c5 !important; opacity: .72; font-size: .72em; }
        #text-stream .char[data-char="virtual-enter"].current { color: #cbd5e1 !important; opacity: 1; }
        #text-stream.multi-line .char[data-char="enter"] { display: inline; width: auto; height: auto; line-height: inherit; margin: 0 .15em 0 0; text-align: left; opacity: .18; white-space: pre; font-size: inherit; }
        #text-stream.multi-line .char[data-char="enter"].current { opacity: 1; color: #cbd5e1 !important; }
        #text-stream.multi-line .char[data-char="enter"].completed { opacity: .08; }
        #text-stream.multi-line .char[data-char="virtual-enter"] { display: inline; width: auto; height: auto; line-height: inherit; margin: 0 .15em 0 0; text-align: left; color: #a8b4c5 !important; opacity: .72; white-space: pre; font-size: inherit; }
        #text-stream.multi-line .char[data-char="virtual-enter"].current { opacity: 1; color: #cbd5e1 !important; }
        #text-stream-container.multi-line + #focus-cursor { display: none; }
        @media (prefers-reduced-motion: reduce) {
            #text-stream-container.multi-line { scroll-behavior: auto; }
            #text-stream.multi-line .char { transition: none; }
        }
        #text-stream .char { flex: 0 0 2rem; }
        #text-stream .char[data-char="enter"] { flex-basis: 2rem; width: 2rem; height: 4rem; justify-content: center; color: #6b7280; }
        #text-stream .char[data-char="tab"] { min-width: 4rem; }
        /* 窄屏不再把固定宽度键盘撑出页面；按键保持同一行比例并完整可见。 */
        @media (max-width: 720px) {
            #game-container { min-width: 0; overflow-x: hidden; }
            #keyboard-area { width: 100%; overflow: hidden; }
            #keyboard { width: 100%; padding: 6px 4px; gap: 4px; }
            #keyboard > div { width: 100%; gap: 2px; }
            #keyboard > div > .key { flex: 1 1 0; width: auto !important; min-width: 0; height: 38px; padding: 0 !important; margin: 0 !important; font-size: 11px; }
            #keyboard > div > .key[data-key="space"] { flex: 5 1 0; }
            #keyboard > div > .key[data-key="shift"], #keyboard > div > .key[data-key="backspace"], #keyboard > div > .key[data-key="capslock"], #keyboard > div > .key[data-key="enter"] { flex: 1.7 1 0; }
            #typing-area { height: 132px; }
            #typing-area:has(#text-stream-container.multi-line) { min-height: 176px; }
            #text-stream-container.multi-line { height: auto; }
            #text-stream { font-size: 2rem; }
            .finger-cue { width: calc(100% - 16px); }
            #game-container header { padding: 10px 72px; font-size: 1.05rem; gap: 16px; }
            #exit-training-btn, #pause-training-btn { top: 8px; font-size: 11px; padding: 6px 4px; }
        }
        .progress-bar { background-color: #374151; }
        .progress-bar-inner { background-color: #22d3ee; transition: width 0.5s ease; }

        /* 课程列表：编辑式、左对齐、内容高度卡片。 */
        #lesson-list {
            --lesson-bg: #111827;
            --lesson-surface: #1d2939;
            --lesson-surface-raised: #243247;
            --lesson-border: #35445a;
            --lesson-text: #f4f7fb;
            --lesson-muted: #aeb9c8;
            --lesson-subtle: #8390a2;
            --lesson-accent: #e8b86f;
            --lesson-accent-soft: rgba(232, 184, 111, .14);
            --lesson-success: #70d69a;
            --lesson-warning: #e9c477;
            --lesson-ease: cubic-bezier(.22, 1, .36, 1);
            align-items: stretch;
            overflow-y: auto;
            overflow-x: hidden;
            background: var(--lesson-bg);
            color: var(--lesson-text);
            padding: clamp(5.25rem, 9vh, 6.5rem) clamp(1rem, 4vw, 2.5rem) 2.5rem;
        }

        #lesson-list .lesson-page-shell {
            width: min(100%, 1160px);
            margin: 0 auto;
            display: flex;
            flex-direction: column;
            gap: clamp(1.25rem, 2.4vw, 2rem);
        }

        #lesson-list .lesson-page-header {
            display: grid;
            gap: .65rem;
            max-width: 780px;
        }

        #lesson-list #lesson-list-title {
            display: flex;
            align-items: flex-start;
            gap: .6rem;
            margin: 0;
            color: var(--lesson-text);
            font-size: clamp(2.25rem, 4.2vw, 3.75rem) !important;
            line-height: 1.05;
            letter-spacing: -.045em;
        }

        #lesson-list .lesson-page-intro {
            margin: 0;
            color: var(--lesson-muted);
            font-size: clamp(1rem, 1.5vw, 1.125rem);
            line-height: 1.6;
            text-align: left;
        }

        #lesson-list #pack-stats-display {
            width: 100%;
            max-width: none;
            margin: 0;
            padding: 0;
            overflow: hidden;
            border: 1px solid var(--lesson-border);
            border-radius: 1rem;
            background: transparent;
        }

        #lesson-list .lesson-stats-grid {
            display: grid;
            grid-template-columns: repeat(4, minmax(0, 1fr));
            gap: 1px;
            background: var(--lesson-border);
        }

        #lesson-list .lesson-stat {
            min-width: 0;
            padding: 1rem 1.1rem;
            background: var(--lesson-surface);
            text-align: left;
        }

        #lesson-list .lesson-stat-value {
            color: var(--lesson-accent) !important;
            font-size: clamp(1.65rem, 2.7vw, 2rem);
            line-height: 1;
            letter-spacing: -.035em;
        }

        #lesson-list .lesson-stat-label {
            display: block;
            margin-top: .45rem;
            color: var(--lesson-muted) !important;
            font-size: .875rem;
            line-height: 1.35;
        }

        #lesson-list #lesson-grid {
            width: 100%;
            max-width: none;
            flex: none;
            display: grid;
            grid-template-columns: repeat(2, minmax(0, 1fr));
            grid-auto-rows: max-content;
            align-items: start;
            gap: 1rem;
            padding: 0;
            overflow: visible;
        }

        #lesson-list .lesson-card {
            min-height: 0;
            height: auto;
            align-self: start;
            display: flex;
            flex-direction: column;
            gap: 1.1rem;
            padding: 1.25rem;
            border: 1px solid var(--lesson-border);
            border-radius: 1rem;
            background: var(--lesson-surface) !important;
            color: var(--lesson-text);
            text-align: left;
            box-shadow: 0 10px 26px rgba(2, 6, 23, .14);
            opacity: 0;
            animation: lesson-card-in .55s var(--lesson-ease) forwards;
            animation-delay: calc(var(--card-index, 0) * 70ms);
            transition: transform .2s var(--lesson-ease), border-color .2s ease, background-color .2s ease, box-shadow .2s ease;
        }

        #lesson-list .lesson-card:hover {
            transform: translateY(-2px);
            border-color: var(--lesson-accent);
            background: var(--lesson-surface-raised) !important;
            box-shadow: 0 14px 30px rgba(2, 6, 23, .22);
        }

        #lesson-list .lesson-card:focus-visible,
        #lesson-list .lesson-back-btn:focus-visible {
            outline: 3px solid var(--lesson-accent);
            outline-offset: 3px;
        }

        #lesson-list .lesson-card-main {
            display: grid;
            gap: .7rem;
        }

        #lesson-list .lesson-card-kicker-row {
            display: flex;
            align-items: baseline;
            justify-content: space-between;
            gap: .75rem;
        }

        #lesson-list .lesson-card-kicker,
        #lesson-list .lesson-card-count {
            font-size: .875rem;
            line-height: 1.35;
        }

        #lesson-list .lesson-card-kicker { color: var(--lesson-muted); }
        #lesson-list .lesson-card-count { color: var(--lesson-accent); font-weight: 700; white-space: nowrap; }

        #lesson-list .lesson-card-title {
            display: flex;
            align-items: flex-start;
            gap: .45rem;
            color: var(--lesson-text);
            font-size: clamp(1.3rem, 2.1vw, 1.65rem);
            font-weight: 700;
            line-height: 1.2;
            letter-spacing: -.025em;
        }

        #lesson-list .lesson-card-objective {
            color: var(--lesson-muted);
            font-size: 1rem;
            line-height: 1.55;
        }

        #lesson-list .lesson-card-meta {
            color: var(--lesson-subtle);
            font-size: .9rem;
            line-height: 1.45;
        }

        #lesson-list .lesson-status {
            display: inline-flex;
            align-items: center;
            align-self: flex-start;
            min-height: 2.75rem;
            gap: .5rem;
            padding: .65rem .85rem;
            border-radius: .7rem;
            font-size: .95rem;
            font-weight: 700;
            line-height: 1.25;
        }

        #lesson-list .lesson-status-icon { font-size: 1rem; }
        #lesson-list .lesson-status-start { color: var(--lesson-accent); background: var(--lesson-accent-soft); }
        #lesson-list .lesson-status-progress { color: var(--lesson-warning); background: rgba(233, 196, 119, .12); }
        #lesson-list .lesson-status-complete { color: var(--lesson-success); background: rgba(112, 214, 154, .12); }

        #lesson-list .lesson-back-btn {
            top: 1rem;
            left: 1rem;
            min-height: 2.75rem;
            padding: .65rem .9rem;
            color: var(--lesson-muted);
            border: 1px solid var(--lesson-border);
            background: var(--lesson-surface);
        }

        #lesson-list .lesson-back-btn:hover {
            color: var(--lesson-text);
            border-color: var(--lesson-accent);
            background: var(--lesson-surface-raised);
        }

        @keyframes lesson-card-in {
            from { opacity: 0; transform: translateY(12px); }
            to { opacity: 1; transform: translateY(0); }
        }

        @media (max-width: 767px) {
            #lesson-list {
                padding: 5rem 1rem 2rem;
            }

            #lesson-list .lesson-page-shell { gap: 1.25rem; }
            #lesson-list #lesson-list-title { font-size: 2.25rem !important; }
            #lesson-list .lesson-page-intro { font-size: 1rem; }
            #lesson-list .lesson-stats-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
            #lesson-list .lesson-stat { padding: .9rem; }
            #lesson-list .lesson-stat-label { font-size: .875rem; }
            #lesson-list #lesson-grid { grid-template-columns: minmax(0, 1fr); gap: .75rem; }
            #lesson-list .lesson-card { padding: 1.1rem; border-radius: .85rem; }
            #lesson-list .lesson-card-title { font-size: 1.35rem; }
            #lesson-list .lesson-card-objective { font-size: 1rem; }
            #lesson-list .lesson-card-meta { font-size: .875rem; }
            #lesson-list .lesson-back-btn { top: .75rem; left: .75rem; }
        }

        @media (prefers-reduced-motion: reduce) {
            #lesson-list .lesson-card {
                animation: none;
                opacity: 1;
                transition: none;
            }

            #lesson-list .lesson-card:hover { transform: none; }
        }