/* 恢复原有页面结构，只做手机端适配；登录状态由 auth-guard.js 显示在右上角。 */
:root{color-scheme:light;--bg:#f4f5f7;--bg-elev:#fff;--bg-muted:#eef0f3;--text:#17191f;--muted:#5c6370;--line:#e3e6ed;--brand:#0f6e62;--brand-strong:#0c574e;--brand-soft:#e6f4f1;--on-brand:#fff;--focus:#0f6e62;--header-bg:#f7faf9;--logo-sheet:#dff3ef;--logo-fold:#fff;--shadow:0 1px 2px rgba(23,25,31,.04),0 10px 28px rgba(23,25,31,.05);--radius:14px;--radius-sm:10px;--font:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Noto Sans CJK SC",sans-serif}.site-header{position:sticky;top:0;z-index:30;display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:8px 24px;padding:12px 28px;background:var(--header-bg);border-bottom:1px solid var(--line);backdrop-filter:none}.brand{display:flex;align-items:center;gap:12px;min-height:48px;color:inherit;text-decoration:none}.logo{color:var(--brand);width:40px;height:40px}.brand-name{font-size:1.08rem;font-weight:750;color:var(--text)}.brand-kicker{font-size:.75rem;color:var(--brand)}.site-nav{display:flex;flex-wrap:wrap;align-items:center;gap:8px 18px}.nav-link{min-height:44px;padding:0 12px;border-radius:999px;color:var(--muted);font-size:.94rem}.nav-link.active,.nav-link[aria-current=page]{background:var(--brand-soft);color:var(--brand-strong)}.nav-link.subject-link{padding:0 14px}.nav-link.subject-link.on{background:var(--brand);color:#fff}.subject-switch{background:var(--bg-muted)}.home-workbench{max-width:none;padding:0}.workbench-hero,.path-section,.stats-section,.grades-section{all:revert}.learning-link{display:inline-flex}
@media(max-width:720px){.site-header{padding:10px 14px 8px;gap:4px 12px}.brand{gap:10px;min-height:44px}.logo{width:34px;height:34px}.brand-name{font-size:1.02rem}.brand-kicker{font-size:.72rem}.site-nav{flex:1 1 100%;justify-content:space-between;gap:4px 8px;overflow-x:auto}.nav-link{padding:0 8px;font-size:.9rem;white-space:nowrap}.nav-link.subject-link{padding:0 12px}.home{padding:24px 16px 40px}.hero{padding:28px 20px}.hero h1{font-size:clamp(2rem,9vw,3.2rem);line-height:1.15}.hero .lede{font-size:1rem}.hero-actions{display:flex;flex-wrap:wrap;gap:10px}.hero-actions .btn{flex:1 1 180px}.steps{grid-template-columns:1fr;gap:12px}.stat-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.grade-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.section-title{font-size:1.55rem}.site-footer{padding:14px 16px 18px}}