:root{--bg:#f7f6ff;--card:#fff;--ink:#1d1b38;--muted:#6b6890;--line:#e6e3f7;--brand:#6d5efc;--soft:#efedff}
@media (prefers-color-scheme:dark){:root{--bg:#121126;--card:#1c1a38;--ink:#f1f0ff;--muted:#a9a6cf;--line:#2e2b55;--soft:#25224a}}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.6 "Be Vietnam Pro",system-ui,sans-serif}
a{color:inherit}
.top{position:sticky;top:0;z-index:5;display:flex;align-items:center;gap:16px;padding:12px 20px;background:color-mix(in srgb,var(--card) 88%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.logo{font-weight:800;font-size:20px;text-decoration:none}.logo b{color:var(--brand)}.dot{color:#ff7a45}
.top nav{margin-left:auto;display:flex;gap:4px}.top nav a{text-decoration:none;padding:6px 12px;border-radius:99px;font-weight:600;font-size:14px;color:var(--muted)}
.top nav a.on{background:var(--soft);color:var(--ink)}
main{max-width:1080px;margin:0 auto;padding:28px 16px 60px}
.foot{text-align:center;color:var(--muted);font-size:13px;padding:24px 16px;border-top:1px solid var(--line)}
h1{font-size:clamp(28px,5vw,44px);line-height:1.15;margin:.2em 0}
h2{font-size:24px;margin:1.6em 0 .5em}h3{margin:.2em 0}
.eyebrow{text-transform:uppercase;letter-spacing:.08em;font-size:12px;font-weight:700;color:var(--muted)}
.muted{color:var(--muted)}
.hero{border-radius:28px;padding:32px;background:linear-gradient(135deg,#6d5efc,#a35cff 55%,#ff7a45);color:#fff}
.hero .eyebrow{color:#fff;opacity:.85}.hero p{max-width:640px;opacity:.95}
.grid{display:grid;gap:16px;grid-template-columns:repeat(auto-fill,minmax(300px,1fr))}
.card{background:var(--card);border:1px solid var(--line);border-radius:20px;padding:20px}
a.card{text-decoration:none;display:block;transition:transform .15s}a.card:hover{transform:translateY(-3px)}
.chip{display:inline-block;font-size:12px;font-weight:700;padding:3px 10px;border-radius:99px;background:var(--soft);margin:2px 4px 2px 0}
.emoji{font-size:34px}
.q{font-weight:600;font-size:18px}
.band{border-left:5px solid var(--c,var(--brand));padding:14px 18px;border-radius:14px;background:var(--card);border-top:1px solid var(--line);border-right:1px solid var(--line);border-bottom:1px solid var(--line);margin:10px 0}
.band .eyebrow{color:var(--c,var(--brand))}
.concepts{display:grid;gap:10px;grid-template-columns:repeat(auto-fill,minmax(230px,1fr))}
.concepts div{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:12px}
.lessonrow{display:flex;gap:14px;align-items:flex-start}
.num{flex:none;width:40px;height:40px;border-radius:12px;display:grid;place-items:center;font-weight:800;color:#fff;background:var(--c,var(--brand))}
.act{display:flex;gap:12px;padding:14px;border-radius:14px;background:var(--card);border:1px solid var(--line);margin:8px 0}
.tag{flex:none;font-size:11px;font-weight:800;color:#fff;border-radius:8px;padding:4px 8px;height:max-content;min-width:96px;text-align:center}
.crumb{font-size:14px;color:var(--muted);margin-bottom:8px}.crumb a{text-decoration:none;font-weight:600}
.pager{display:flex;justify-content:space-between;gap:10px;margin-top:24px}
.btn{display:inline-block;text-decoration:none;font-weight:700;padding:10px 16px;border-radius:12px;background:var(--brand);color:#fff}
.btn.ghost{background:var(--soft);color:var(--ink)}
table{width:100%;border-collapse:collapse;background:var(--card);border-radius:14px;overflow:hidden}
td,th{text-align:left;padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:top}
th{width:160px}
.cycle{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.cycle div{border-radius:16px;padding:14px;color:#fff}
@media (max-width:640px){.cycle{grid-template-columns:1fr 1fr}.hero{padding:22px}th{width:110px}.tag{min-width:76px}}
.tree{font-size:15px}.tree .node{border:2px dashed var(--line);border-radius:16px;padding:12px 14px;margin:8px 0;background:var(--card)}
.tree .node .node{margin-left:18px}
.tree .lbl{font-weight:800}.tree .lbl small{font-weight:600;color:var(--muted);margin-left:6px}
.tree .ex{font-size:14px;color:var(--muted)}