:root{--bg:#f4f5fc;--panel:#fff;--inset:#f2f3fb;--chip:#eef0fb;--border:#e5e8f4;--text:#242744;--muted:#7a7e9c;--soft-text:#4a4e72;--accent:#6d4bff;--accent2:#8b6dff;--good:#12b886;--warn:#f0820e;--bad:#ef4d6a;--gold:#f5ad12;--hint-bg:#fff5e0;--hint-text:#9a6500;--fail-bg:#fdeef2;--shadow:0 6px 20px rgba(70,60,130,.08);--shadow-sm:0 3px 10px rgba(70,60,130,.07)}*{box-sizing:border-box}body,html{margin:0;padding:0}body{background:radial-gradient(1100px 620px at 82% -12%,#efeaff 0,#f4f5fc 58%) fixed;color:var(--text);font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,sans-serif;-webkit-font-smoothing:antialiased}a{color:inherit;text-decoration:none}button{font-family:inherit}::-webkit-scrollbar{width:10px;height:10px}::-webkit-scrollbar-thumb{background:#d7daea;border-radius:8px}::-webkit-scrollbar-track{background:transparent}.shell{display:grid;grid-template-columns:240px 1fr;min-height:100vh}.sidebar{position:-webkit-sticky;position:sticky;top:0;height:100vh;background:#ffffffcc;-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);border-right:1px solid var(--border);display:flex;flex-direction:column;padding:16px 12px;gap:4px}.brand{font-weight:850;font-size:21px;padding:6px 10px 16px;letter-spacing:.2px}.nav-item{display:flex;align-items:center;gap:11px;padding:11px 12px;border-radius:12px;cursor:pointer;color:var(--muted);font-weight:650;font-size:15px;border:0;background:transparent;width:100%;text-align:left}.nav-item:hover{background:#f0edff;color:var(--text)}.nav-item.active{background:linear-gradient(90deg,#6d4bff,#8b6dff);color:#fff;box-shadow:var(--shadow-sm)}.nav-ico{width:22px;text-align:center;font-size:17px}.nav-spacer{flex:1 1}.main{padding:26px 30px 96px;width:100%;max-width:1080px;margin:0 auto}.bottom-tabs{display:none}@media (max-width:860px){.shell{grid-template-columns:1fr}.sidebar{display:none}.main{padding:16px 14px 92px}.bottom-tabs{display:flex;position:fixed;bottom:0;left:0;right:0;background:#fffffff2;border-top:1px solid var(--border);justify-content:space-around;padding:7px 0 9px;z-index:60;box-shadow:0 -4px 20px rgba(70,60,130,.08)}.tab{display:flex;flex-direction:column;align-items:center;gap:3px;font-size:11px;color:var(--muted);cursor:pointer;background:none;border:0}.tab.active{color:var(--accent)}}.fade{animation:fade .24s ease both}@keyframes fade{0%{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}.tile{border-radius:16px;padding:16px 14px;text-align:center;color:#fff;box-shadow:var(--shadow-sm)}.tile .v{font-size:24px;font-weight:850;line-height:1.1}.tile .l{font-size:12px;opacity:.92;font-weight:600}.tile .ico{font-size:22px}.tile.violet{background:linear-gradient(135deg,#7b5cff,#a98bff)}.tile.gold{background:linear-gradient(135deg,#f5a623,#ffce54)}.tile.flame{background:linear-gradient(135deg,#ff6a3d,#ffa14d)}.tile.teal{background:linear-gradient(135deg,#12b9a6,#46dca0)}.lesson{max-width:760px;margin:0 auto}.lesson h1{font-size:28px;line-height:1.2}.lesson .sec{background:var(--panel);border:1px solid var(--border);border-radius:16px;padding:22px 30px;margin:0;box-shadow:var(--shadow-sm)}.lesson .label{text-transform:uppercase;font-size:11px;letter-spacing:1.4px;color:var(--accent);font-weight:750;margin-bottom:12px}.prose{font-family:Georgia,Iowan Old Style,Times New Roman,serif;font-size:18px;line-height:1.82;color:#3a3d57;letter-spacing:.1px}.prose p{margin:0 0 15px}.prose p:last-child{margin-bottom:0}.prose strong{color:#16182b;font-weight:700}.prose em{color:#9a6500;font-style:italic}.prose .katex{font-size:1.08em;color:#2b2e4a}@media (max-width:860px){.lesson .sec{padding:18px}.prose{font-size:17px}}.lwrap{max-width:1040px;margin:0 auto;padding:22px 20px 60px}.lnav{display:flex;align-items:center;gap:14px;padding:6px 0 40px}.hero{text-align:center;padding:30px 0 10px}.hero h1{font-size:clamp(34px,6vw,60px);line-height:1.05;margin:0 0 16px;font-weight:850;letter-spacing:-.5px;color:#1c1e36}.hero .grad{background:linear-gradient(120deg,#6d4bff,#a24bff 50%,#d6489f);-webkit-background-clip:text;background-clip:text;color:transparent}.hero p{font-size:clamp(16px,2.2vw,20px);color:var(--muted);max-width:600px;margin:0 auto 26px}.feat-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));grid-gap:16px;gap:16px;margin-top:48px}.cta{background:linear-gradient(135deg,#6d4bff,#8b6dff);color:#fff;border:0;border-radius:14px;padding:14px 28px;font-weight:800;font-size:17px;cursor:pointer;box-shadow:var(--shadow)}.cta:hover{filter:brightness(1.06)}.ghost{background:#fff;color:var(--accent);border:1.5px solid var(--border);border-radius:14px;padding:13px 24px;font-weight:700;font-size:16px;cursor:pointer}