:root{--c-bg:#090d1a;--c-bg-soft:#0f1425;--c-surface:#1e293ba6;--c-surface-hover:#28374bbf;--c-border:#94a3b81a;--c-border-glow:#e2a84633;--c-text:#f1f5f9;--c-text-dim:#94a3b8;--c-accent:#e2a846;--c-accent-glow:#f59e0b;--c-accent-2:#3b82f6;--c-danger:#f87171;--c-physics:#2dd4bf;--radius-xl:1.75rem;--radius-lg:1.25rem;--radius-md:.75rem;--radius-sm:.5rem}*,:before,:after{box-sizing:border-box;margin:0;padding:0}html{color:var(--c-text);background:var(--c-bg);-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;font-size:18px}body{background:radial-gradient(ellipse 80% 60% at 50% -10%, #3b82f614 0%, transparent 60%), radial-gradient(ellipse 60% 50% at 80% 80%, #e2a8460f 0%, transparent 50%), linear-gradient(160deg, var(--c-bg) 0%, #0c1122 40%, var(--c-bg-soft) 100%);background-attachment:fixed;min-height:100vh;font-family:PingFang SC,Microsoft YaHei,Hiragino Sans GB,WenQuanYi Micro Hei,system-ui,-apple-system,sans-serif}#app{max-width:1200px;margin:0 auto;padding:3rem 2rem}.hero{text-align:center;padding:1.5rem 0 2rem}.hero-title{letter-spacing:-.02em;background:linear-gradient(135deg, var(--c-text) 0%, var(--c-accent) 50%, var(--c-accent-2) 100%);-webkit-text-fill-color:transparent;-webkit-background-clip:text;background-clip:text;font-size:2rem;font-weight:700}.tabs{flex-wrap:wrap;justify-content:center;gap:.5rem;padding:0 0 2rem;display:flex}.tab{color:var(--c-text-dim);background:var(--c-surface);border:1px solid var(--c-border);border-radius:var(--radius-lg);cursor:pointer;-webkit-backdrop-filter:blur(12px);padding:.45rem 1.1rem;font-family:inherit;font-size:.85rem;font-weight:500;transition:background .2s,border-color .2s,color .2s}.tab:hover{color:var(--c-text);border-color:#94a3b840}.tab.active{color:var(--c-accent);border-color:var(--c-border-glow);background:#e2a8461f}.course-grid{grid-template-columns:repeat(auto-fill,minmax(340px,1fr));gap:1.25rem;padding:1rem 0 3rem;display:grid}.course-card{background:var(--c-surface);-webkit-backdrop-filter:blur(16px);border:1px solid var(--c-border);border-radius:var(--radius-xl);color:inherit;cursor:pointer;flex-direction:column;gap:.5rem;padding:1.5rem;text-decoration:none;transition:transform .25s,box-shadow .25s,border-color .25s;display:flex;position:relative}.course-card:hover{background:var(--c-surface-hover);border-color:var(--c-border-glow);transform:translateY(-4px);box-shadow:0 8px 32px #0000004d,0 0 0 1px #e2a8461a}.card-chapter{color:var(--c-text-dim);letter-spacing:.04em;font-family:Georgia,Times New Roman,Noto Serif SC,Source Han Serif SC,SimSun,serif;font-size:.95rem;position:absolute;top:1rem;right:1.25rem}.card-title{color:var(--c-text);padding-right:4rem;font-size:1.25rem;font-weight:700;line-height:1.3}.card-desc{color:var(--c-text-dim);flex:1;font-size:.85rem;line-height:1.65}.card-footer{border-top:1px solid var(--c-border);align-items:center;gap:.5rem;padding-top:.5rem;display:flex}.card-tags{flex-wrap:wrap;gap:.4rem;display:flex}.tag{color:var(--c-accent-2);letter-spacing:.02em;background:#3b82f61f;border-radius:999px;padding:.2rem .6rem;font-size:.7rem;font-weight:500;display:inline-block}.group-empty{text-align:center;color:var(--c-text-dim);background:var(--c-surface);border:1px dashed var(--c-border);border-radius:var(--radius-lg);opacity:.7;grid-column:1/-1;padding:3rem 1rem;font-size:.9rem}.footer{text-align:center;color:var(--c-text-dim);opacity:.6;padding:2rem 0 1rem;font-size:.8rem}@media (width<=768px){#app{padding:2rem 1rem}.group-courses{grid-template-columns:1fr}.hero-title{font-size:1.8rem}}