:root {
  --ink:#1d1d1f;
  --muted:#6e6e73;
  --soft:#f5f5f7;
  --line:#e5e5e7;
  --accent:#0071e3;
  --accent-rgb:0,113,227;
  --font:-apple-system,BlinkMacSystemFont,"SF Pro Text","Helvetica Neue",Arial,sans-serif;
}
* { box-sizing:border-box; }
html { scroll-behavior:smooth; }
body { margin:0; color:var(--ink); background:#fff; font:16px/1.55 var(--font); letter-spacing:-.011em; text-rendering:optimizeLegibility; }
a { color:inherit; text-decoration:none; }
.nav { position:fixed; z-index:20; inset:0 0 auto; height:58px; border-bottom:1px solid rgba(0,0,0,.05); background:rgba(255,255,255,.86); backdrop-filter:blur(22px); }
.nav-inner { width:min(1120px,calc(100% - 40px)); height:100%; margin:auto; display:flex; align-items:center; justify-content:space-between; gap:24px; }
.brand { display:flex; align-items:center; gap:10px; font-size:14px; font-weight:650; }
.brand-mark { width:28px; height:28px; display:grid; place-items:center; border-radius:9px; color:#fff; background:var(--accent); font-size:17px; }
.back { color:var(--muted); font-size:14px; transition:color .2s; }
.back:hover { color:var(--ink); }
.author { color:var(--muted); font-size:13px; white-space:nowrap; }
.container { width:min(1120px,calc(100% - 40px)); margin-inline:auto; }
.hero { overflow:hidden; padding:132px 0 72px; background:linear-gradient(180deg,rgba(var(--accent-rgb),.055),rgba(var(--accent-rgb),0) 68%); }
.hero-grid { display:grid; grid-template-columns:minmax(0,1fr) 250px; align-items:end; gap:56px; }
.eyebrow { margin:0; color:var(--accent); font-size:14px; font-weight:700; letter-spacing:.03em; }
h1 { max-width:850px; margin:18px 0 0; font-size:clamp(48px,7.4vw,82px); line-height:.96; letter-spacing:-.06em; font-weight:650; }
h1 span { color:var(--accent); }
.lead { max-width:760px; margin:26px 0 0; color:var(--muted); font-size:clamp(19px,2.2vw,23px); line-height:1.55; }
.hero-letter { width:220px; aspect-ratio:1; display:grid; place-items:center; border:1px solid rgba(var(--accent-rgb),.18); border-radius:50%; color:var(--accent); background:rgba(255,255,255,.6); font-size:124px; font-weight:620; letter-spacing:-.08em; box-shadow:0 28px 70px rgba(var(--accent-rgb),.09); }
.block-switch { display:grid; grid-template-columns:repeat(5,1fr); gap:9px; margin-top:54px; }
.block-switch a { min-height:54px; display:flex; align-items:center; gap:9px; padding:12px 15px; border:1px solid var(--line); border-radius:16px; color:var(--muted); background:#fff; font-size:14px; transition:.2s; }
.block-switch a:hover { transform:translateY(-1px); border-color:#c7c7cc; color:var(--ink); }
.block-switch a[aria-current="page"] { border-color:rgba(var(--accent-rgb),.4); color:var(--accent); background:rgba(var(--accent-rgb),.055); }
.block-switch b { color:inherit; font-size:16px; }
.topics { padding:78px 0 90px; border-top:1px solid var(--line); }
.section-head { display:flex; align-items:end; justify-content:space-between; gap:36px; margin-bottom:30px; }
.section-head h2 { margin:9px 0 0; font-size:clamp(34px,5vw,52px); line-height:1; letter-spacing:-.048em; font-weight:650; }
.section-copy { max-width:470px; margin:0; color:var(--muted); font-size:16px; line-height:1.65; }
.topic-grid { display:grid; grid-template-columns:repeat(auto-fit,minmax(150px,1fr)); gap:10px; }
.topic { min-height:150px; padding:20px; border:1px solid var(--line); border-radius:22px; background:#fff; }
.topic b { display:block; color:var(--accent); font-size:13px; letter-spacing:.025em; }
.topic span { display:block; margin-top:25px; font-size:16px; line-height:1.35; font-weight:600; }
.summary { padding:0 0 90px; background:#fff; }
.summary-card { display:grid; grid-template-columns:minmax(0,1fr) auto; align-items:center; gap:36px; padding:32px; border:1px solid rgba(var(--accent-rgb),.25); border-radius:28px; background:linear-gradient(135deg,rgba(var(--accent-rgb),.075),rgba(var(--accent-rgb),.025)); }
.summary-meta { display:flex; align-items:center; gap:18px; }
.summary-mark { width:56px; height:56px; flex:0 0 auto; display:grid; place-items:center; border-radius:17px; color:#fff; background:var(--accent); font-size:25px; font-weight:700; }
.summary-kicker { display:block; color:var(--accent); font-size:13px; font-weight:700; letter-spacing:.025em; }
.summary-card h2 { margin:6px 0 0; font-size:clamp(27px,4vw,38px); line-height:1.08; letter-spacing:-.04em; }
.summary-card p { max-width:720px; margin:14px 0 0; color:var(--muted); line-height:1.65; }
.summary-open { min-width:190px; min-height:52px; display:flex; align-items:center; justify-content:space-between; gap:20px; padding:13px 16px; border-radius:15px; color:#fff; background:var(--accent); font-size:14px; font-weight:650; transition:transform .2s ease,filter .2s ease; }
.summary-open:hover { transform:translateY(-1px); filter:brightness(1.04); }
.resources { padding:94px 0 106px; background:var(--soft); }
.resource-grid { display:grid; grid-template-columns:repeat(2,1fr); gap:16px; }
.resource-card { min-height:280px; display:flex; flex-direction:column; padding:28px; border:1px solid var(--line); border-radius:27px; background:#fff; box-shadow:0 20px 55px rgba(0,0,0,.045); transition:transform .22s ease,box-shadow .22s ease; }
.resource-card:hover { transform:translateY(-3px); box-shadow:0 27px 66px rgba(0,0,0,.075); }
.card-meta { display:flex; align-items:center; justify-content:space-between; gap:14px; color:var(--muted); font-size:13px; }
.card-source { color:var(--accent); font-weight:700; letter-spacing:.02em; }
.resource-card h3 { margin:34px 0 0; font-size:28px; line-height:1.08; letter-spacing:-.037em; }
.resource-card p { max-width:520px; margin:13px 0 0; color:var(--muted); line-height:1.65; }
.tags { display:flex; flex-wrap:wrap; gap:7px; margin-top:auto; padding-top:26px; }
.tag { padding:6px 10px; border-radius:999px; background:var(--soft); color:#4b4b50; font-size:12px; }
.open { margin-top:18px; color:var(--accent); font-weight:650; }
.exercises { padding:96px 0 106px; color:#f5f5f7; background:#0b0b0d; }
.exercises .eyebrow { color:#7ab8ff; }
.exercises .section-copy { color:#a1a1a6; }
.exercise-card { display:grid; grid-template-columns:minmax(0,1fr) auto; gap:42px; padding:34px; border:1px solid #2c2c2e; border-radius:28px; background:#161618; }
.exercise-kicker { color:#7ab8ff; font-size:13px; font-weight:700; letter-spacing:.025em; }
.exercise-card h3 { margin:18px 0 0; font-size:clamp(29px,4vw,40px); line-height:1.05; letter-spacing:-.04em; }
.exercise-card p { max-width:670px; margin:15px 0 0; color:#a1a1a6; line-height:1.7; }
.exercise-data { display:flex; flex-wrap:wrap; gap:9px; margin-top:25px; }
.exercise-data span { padding:7px 11px; border:1px solid #343438; border-radius:999px; color:#c7c7cc; font-size:13px; }
.download-stack { width:220px; display:flex; flex-direction:column; justify-content:center; gap:10px; }
.download { min-height:50px; display:flex; align-items:center; justify-content:space-between; gap:14px; padding:12px 15px; border:1px solid #3a3a3c; border-radius:15px; background:#1d1d1f; color:#fff; font-size:14px; font-weight:650; transition:.2s; }
.download:first-child { border-color:var(--accent); background:var(--accent); }
.download:hover { transform:translateY(-1px); filter:brightness(1.05); }
.empty-exercises { padding:42px; border:1px solid #2c2c2e; border-radius:28px; background:#161618; text-align:center; }
.empty-exercises strong { display:block; font-size:24px; letter-spacing:-.025em; }
.empty-exercises p { max-width:600px; margin:10px auto 0; color:#a1a1a6; }
.next { padding:78px 0; background:#fff; }
.next-row { display:flex; align-items:center; justify-content:space-between; gap:24px; padding:28px 0; border-block:1px solid var(--line); }
.next-row span { color:var(--muted); font-size:14px; }
.next-row a { color:var(--accent); font-size:20px; font-weight:650; }
.legal { max-width:920px; margin:0 auto; padding:30px 20px; color:#8e8e93; text-align:center; font-size:12px; line-height:1.6; }
footer { padding:30px 20px; border-top:1px solid var(--line); color:var(--muted); text-align:center; font-size:14px; }
@media (max-width:900px) {
  .author { display:none; }
  .hero-grid { grid-template-columns:1fr 170px; gap:32px; }
  .hero-letter { width:160px; font-size:92px; }
  .block-switch { grid-template-columns:repeat(3,1fr); }
  .topic-grid { grid-template-columns:repeat(3,1fr); }
  .exercise-card { grid-template-columns:1fr; }
  .summary-card { grid-template-columns:1fr; }
  .summary-open { width:100%; }
  .download-stack { width:100%; display:grid; grid-template-columns:1fr 1fr; }
}
@media (max-width:650px) {
  .nav-inner,.container { width:calc(100% - 24px); }
  .back { margin-left:auto; }
  .hero { padding:108px 0 58px; }
  .hero-grid { grid-template-columns:1fr; }
  .hero-letter { display:none; }
  h1 { font-size:clamp(48px,15vw,68px); }
  .block-switch { grid-template-columns:1fr 1fr; margin-top:40px; }
  .block-switch a:last-child { grid-column:1/-1; }
  .topics,.resources,.exercises { padding:72px 0 80px; }
  .summary { padding:0 0 72px; }
  .section-head { align-items:start; flex-direction:column; }
  .topic-grid,.resource-grid { grid-template-columns:1fr; }
  .topic { min-height:auto; }
  .topic span { margin-top:16px; }
  .exercise-card { padding:25px; }
  .summary-card { padding:24px; }
  .download-stack { grid-template-columns:1fr; }
  .next-row { align-items:flex-start; flex-direction:column; }
}
@media (prefers-reduced-motion:reduce) { *,*::before,*::after { scroll-behavior:auto!important; transition-duration:.01ms!important; } }