:root{--primary: #4f46e5;--primary-light: #eef2ff;--success: #16a34a;--danger: #dc2626;--warning: #d97706;--bg: #f4f5f7;--card: #ffffff;--text: #1f2937;--text-2: #6b7280;--border: #e5e7eb;--radius: 14px;--nav-h: 60px}*{box-sizing:border-box;margin:0;padding:0}html{-webkit-text-size-adjust:100%}body{font-family:-apple-system,BlinkMacSystemFont,PingFang SC,Hiragino Sans GB,Microsoft YaHei,Segoe UI,sans-serif;background:var(--bg);color:var(--text);line-height:1.6}#app{max-width:520px;margin:0 auto;min-height:100vh;background:var(--bg)}.page{padding:16px 16px calc(var(--nav-h) + 24px + env(safe-area-inset-bottom))}.card{background:var(--card);border-radius:var(--radius);padding:16px;margin-bottom:12px;box-shadow:0 1px 3px #0000000f}.section-title{font-size:17px;font-weight:700;margin:20px 0 10px;display:flex;align-items:center;gap:8px}.section-title .badge{font-size:12px;font-weight:600;background:var(--danger);color:#fff;border-radius:999px;padding:1px 9px}.btn{display:block;width:100%;border:none;border-radius:12px;padding:13px 16px;font-size:16px;font-weight:600;cursor:pointer;text-align:center;text-decoration:none;transition:opacity .15s}.btn:active{opacity:.85}.btn-primary{background:var(--primary);color:#fff}.btn-outline{background:#fff;color:var(--primary);border:1.5px solid var(--primary)}.btn-ghost{background:transparent;color:var(--text-2)}.btn+.btn{margin-top:10px}.btn:disabled{opacity:.45;cursor:not-allowed}.tag{display:inline-block;font-size:12px;padding:2px 10px;border-radius:999px;background:var(--primary-light);color:var(--primary);font-weight:600}.muted{color:var(--text-2);font-size:13px}.lesson-item{display:flex;align-items:center;gap:12px;padding:14px 16px;background:var(--card);border-radius:var(--radius);margin-bottom:10px;text-decoration:none;color:inherit;box-shadow:0 1px 3px #0000000f}.lesson-item .dot{width:10px;height:10px;border-radius:50%;flex-shrink:0}.lesson-item .info{flex:1;min-width:0}.lesson-item .title{font-size:15px;font-weight:600;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.lesson-item .sub{font-size:12px;color:var(--text-2);margin-top:2px}.lesson-item .arrow{color:var(--text-2);font-size:18px}.lesson-item.done{opacity:.75}.status-icon{font-size:18px;flex-shrink:0}.progress{height:8px;background:var(--border);border-radius:999px;overflow:hidden}.progress>i{display:block;height:100%;border-radius:999px;background:var(--primary);transition:width .3s}pre.code{background:#1e293b;color:#e2e8f0;border-radius:10px;padding:12px 14px;font-size:13px;line-height:1.55;overflow-x:auto;margin:10px 0;font-family:Cascadia Code,Consolas,Courier New,monospace;white-space:pre}.app-header{position:sticky;top:0;z-index:20;background:var(--primary);color:#fff;padding:14px 16px;padding-top:calc(14px + env(safe-area-inset-top))}.app-header h1{font-size:18px;font-weight:700}.app-header .sub{font-size:12px;opacity:.85;margin-top:2px}.bottom-nav{position:fixed;bottom:0;left:50%;transform:translate(-50%);width:100%;max-width:520px;height:calc(var(--nav-h) + env(safe-area-inset-bottom));padding-bottom:env(safe-area-inset-bottom);background:#fff;border-top:1px solid var(--border);display:flex;z-index:30}.bottom-nav a{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:2px;text-decoration:none;color:var(--text-2);font-size:11px;position:relative}.bottom-nav a .icon{font-size:20px}.bottom-nav a.active{color:var(--primary);font-weight:600}.bottom-nav .nav-badge{position:absolute;top:6px;left:calc(50% + 6px);background:var(--danger);color:#fff;font-size:10px;min-width:16px;height:16px;border-radius:999px;display:flex;align-items:center;justify-content:center;padding:0 4px}.quiz-option{display:block;width:100%;text-align:left;background:#fff;border:1.5px solid var(--border);border-radius:12px;padding:13px 14px;font-size:15px;margin-bottom:10px;cursor:pointer}.quiz-option.selected{border-color:var(--primary);background:var(--primary-light)}.quiz-option.correct{border-color:var(--success);background:#f0fdf4}.quiz-option.wrong{border-color:var(--danger);background:#fef2f2}.explain{border-radius:12px;padding:12px 14px;font-size:14px;margin:12px 0}.explain.ok{background:#f0fdf4;border:1px solid #bbf7d0}.explain.no{background:#fef2f2;border:1px solid #fecaca}.stat-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px}.stat-cell{background:var(--card);border-radius:var(--radius);padding:14px;text-align:center;box-shadow:0 1px 3px #0000000f}.stat-cell .num{font-size:26px;font-weight:800;color:var(--primary)}.stat-cell .label{font-size:12px;color:var(--text-2);margin-top:2px}.bar-chart{display:flex;align-items:flex-end;gap:8px;height:90px;padding:0 4px}.bar-chart .bar{flex:1;display:flex;flex-direction:column;align-items:center;gap:4px;height:100%;justify-content:flex-end}.bar-chart .bar i{width:100%;max-width:28px;background:var(--primary);border-radius:6px 6px 0 0;min-height:3px;display:block}.bar-chart .bar span{font-size:10px;color:var(--text-2)}.empty{text-align:center;color:var(--text-2);padding:28px 0;font-size:14px}@media(min-width:560px){body{background:#e8eaf0}#app{box-shadow:0 0 24px #00000014}}