/* The Learners' Alley library website, in the books' look: warm paper, teal display type, amber accents, and each
   course's land colour at the foot of its pages (as on its covers and introduction deck). Written by build-site.js. */
:root{
  --paper:#efe4c8; --paper-hi:#f6efdc; --card:#f8f2e1; --line:#ddcfa9; --line-2:#cdbd92;
  --ink:#18262e; --ink-2:#4a585e; --teal:#24525a; --teal-2:#2f6a73; --amber:#9a6a1c;
  --land:#24525a; --deep:#173a40;
  --f-display:"Urbanist", "Arial Black", system-ui, sans-serif; --f-body:"IBM Plex Sans", "Segoe UI", system-ui, sans-serif;
  color-scheme:light;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{margin:0;min-height:100vh;display:flex;flex-direction:column;color:var(--ink);font-family:var(--f-body);font-size:17px;line-height:1.55;
  background:var(--paper) radial-gradient(ellipse 90% 60% at 30% 0%, var(--paper-hi) 0%, transparent 70%) no-repeat}
a{color:inherit}
img{display:block;max-width:100%;height:auto}
.wrap{width:100%;max-width:1160px;margin:0 auto;padding:0 28px}
body > .wrap{flex:1}
:focus-visible{outline:3px solid var(--amber);outline-offset:2px;border-radius:6px}

/* top bar */
.top{display:flex;align-items:center;justify-content:space-between;gap:18px;padding:22px 0 10px}
.brand{display:flex;align-items:center;gap:12px;text-decoration:none}
.logo{width:44px;height:44px;flex:none}
.brand span{display:flex;flex-direction:column;line-height:1.1}
.brand b{font-family:var(--f-display);font-weight:800;font-size:14px;letter-spacing:.2em;text-transform:uppercase;color:var(--teal)}
.brand small{font-weight:500;font-size:13px;color:var(--ink-2);margin-top:3px}
.courses{display:flex;gap:4px;background:#00000008;border-radius:14px;padding:4px}
.courses a{font-family:var(--f-display);font-weight:700;font-size:15.5px;text-decoration:none;color:var(--ink-2);padding:7px 14px;border-radius:10px;white-space:nowrap}
.courses a:hover{color:var(--ink);background:#ffffff80}
.courses a[aria-current]{background:var(--teal);color:#fff}

/* home: title and the three courses */
.intro{padding:46px 0 34px;max-width:760px}
.intro h1, .hero h1{font-family:var(--f-display);font-weight:800;line-height:.98;letter-spacing:-.01em;color:var(--ink);margin:0}
.intro h1{font-size:76px}
.lead{font-size:20px;color:var(--ink-2);margin:16px 0 0;max-width:620px}
.lead a{color:var(--teal);font-weight:600}
.shelf{display:grid;grid-template-columns:repeat(3, 1fr);gap:24px;padding-bottom:64px}
.course{display:flex;flex-direction:column;background:var(--card);border-radius:24px;overflow:hidden;box-shadow:0 1px 0 var(--line), 0 14px 30px -18px #3a2c0e66;border:1px solid var(--line)}
.course-link{display:flex;flex-direction:column;text-decoration:none;flex:1}
.course .art{aspect-ratio:900 / 1013;background:var(--land);overflow:hidden}
.course .art img{width:100%;height:100%;object-fit:cover;transition:transform .5s ease}
.course-link:hover .art img{transform:scale(1.03)}
.course-txt{padding:20px 22px 6px}
.lvl{font-family:var(--f-display);font-weight:800;font-size:15px;letter-spacing:.16em;text-transform:uppercase;color:var(--amber);margin:0}
.course h2{font-family:var(--f-display);font-weight:800;font-size:34px;line-height:1.05;margin:4px 0 4px;color:var(--teal)}
.exam{margin:0;color:var(--ink-2);font-weight:500}
.counts{margin:10px 0 0;font-size:14.5px;color:var(--ink-2)}
.jump{display:flex;gap:8px;flex-wrap:wrap}
.course .jump{padding:14px 22px 22px}
.jump a{font-family:var(--f-display);font-weight:700;font-size:15px;text-decoration:none;padding:7px 13px;border-radius:10px;background:#ffffff;color:var(--teal);box-shadow:inset 0 0 0 1.5px var(--line-2)}
.jump a:hover{background:var(--teal);color:#fff;box-shadow:none}

/* course page: hero */
.hero{display:grid;grid-template-columns:1.15fr .85fr;gap:40px;align-items:center;padding:30px 0 46px}
.hero .lvl{font-size:16px}
.hero h1{font-size:72px;margin-top:8px}
.hero .exam{font-size:19px;margin-top:8px}
.hero .lead{margin-top:18px}
.hero .jump{margin-top:26px}
.hero .jump a{font-size:16.5px;padding:10px 18px;border-radius:12px}
.hero .jump a:first-child{background:var(--teal);color:#fff;box-shadow:none}
.hero .art{border-radius:26px;overflow:hidden;background:var(--land);box-shadow:0 18px 40px -22px #2b1d0699;max-width:440px;justify-self:end;width:100%}

/* sections */
.blk{padding:34px 0 30px;scroll-margin-top:12px}
.sh{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap;border-top:2px solid var(--line);padding-top:26px}
.sh h2{font-family:var(--f-display);font-weight:800;font-size:40px;line-height:1;margin:0;color:var(--teal)}
.sub{color:var(--ink-2);margin:10px 0 24px;max-width:760px}

/* colour / black-and-white switch */
.ed{display:flex;background:#00000008;border-radius:12px;padding:4px;gap:2px}
.ed button{font:700 15px var(--f-display);border:0;background:transparent;color:var(--ink-2);padding:7px 14px;border-radius:9px;cursor:pointer}
.ed button[aria-pressed="true"]{background:#fff;color:var(--ink);box-shadow:0 1px 3px #0002}

/* books */
.book{display:grid;grid-template-columns:150px 1fr;gap:28px;align-items:start;background:var(--card);border:1px solid var(--line);border-radius:22px;padding:24px;margin-bottom:22px}
.book:not(:has(.cover)){grid-template-columns:1fr}
.cover{width:150px;border-radius:6px;box-shadow:0 1px 0 #0000001a, 0 12px 22px -12px #2b1d06aa;position:sticky;top:20px}
.book h3{font-family:var(--f-display);font-weight:800;font-size:28px;line-height:1.1;margin:0;color:var(--amber)}
.when{margin:4px 0 0;color:var(--ink-2)}
.chips{display:flex;gap:8px;flex-wrap:wrap;margin:12px 0 4px}
.chip{font-family:var(--f-display);font-weight:700;font-size:14.5px;text-decoration:none;padding:6px 12px;border-radius:9px;background:#fff;color:var(--teal);box-shadow:inset 0 0 0 1.5px var(--line-2)}
.chip:hover{box-shadow:inset 0 0 0 1.5px var(--teal)}
.chip.strong{background:var(--teal);color:#fff;box-shadow:none}
.chip.strong:hover{background:var(--teal-2)}
.rows{list-style:none;margin:10px 0 0;padding:0}
.row{display:grid;grid-template-columns:52px 1fr auto;gap:14px;align-items:center;padding:11px 0;border-top:1px solid var(--line)}
.row:first-child{border-top:0}
.num{width:44px;height:44px;border-radius:12px;display:grid;place-items:center;font-family:var(--f-display);font-weight:800;font-size:16px;color:var(--teal);box-shadow:inset 0 0 0 2px var(--teal);background:#ffffff70;line-height:1;text-align:center}
.name{font-family:var(--f-display);font-weight:700;font-size:19px;line-height:1.2;color:var(--ink)}
.acts{display:flex;gap:6px;flex-wrap:wrap;justify-content:flex-end}
.btn{font-family:var(--f-display);font-weight:700;font-size:15px;text-decoration:none;padding:7px 14px;border-radius:10px;background:var(--teal);color:#fff;white-space:nowrap}
.btn:hover{background:var(--teal-2)}
.btn.ghost{background:transparent;color:var(--teal);box-shadow:inset 0 0 0 1.5px var(--line-2)}
.btn.ghost:hover{box-shadow:inset 0 0 0 1.5px var(--teal)}
.later{opacity:.85}
.later .num{color:var(--ink-2);box-shadow:inset 0 0 0 2px var(--line-2)}
.later .name{color:var(--ink-2)}
.soon{font-size:13.5px;font-weight:600;color:var(--ink-2);letter-spacing:.04em}

/* slides */
.decks{display:grid;grid-template-columns:repeat(auto-fill, minmax(250px, 1fr));gap:20px}
.deck{display:flex;flex-direction:column;text-decoration:none;background:var(--card);border:1px solid var(--line);border-radius:18px;overflow:hidden;transition:transform .2s ease, box-shadow .2s ease}
.deck:hover{transform:translateY(-3px);box-shadow:0 14px 26px -16px #2b1d0699}
.deck img{aspect-ratio:16 / 9;width:100%;object-fit:cover;background:var(--land)}
.deck span{display:flex;gap:10px;align-items:center;padding:12px 14px 14px;font-family:var(--f-display);font-weight:700;font-size:17px;line-height:1.2}
.deck i{flex:none;font-style:normal;font-weight:800;font-size:13.5px;color:var(--teal);box-shadow:inset 0 0 0 1.5px var(--teal);border-radius:8px;padding:3px 7px;min-width:32px;text-align:center}

/* problem sets: a card per topic, two columns on wide screens */
.psets{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:1fr 1fr;gap:16px}
.pset{background:var(--card);border:1px solid var(--line);border-radius:18px;padding:16px 20px 18px}
.pt{display:flex;align-items:center;gap:12px;margin-bottom:4px}
.pt .num{width:38px;height:38px;border-radius:10px;font-size:14.5px;flex:none}
.set{display:grid;grid-template-columns:50px 1fr;align-items:start;gap:8px;margin-top:9px}
.set b{font-family:var(--f-display);font-weight:800;font-size:15px;color:var(--amber);line-height:34px}
.set .acts{justify-content:flex-start}

/* the land at the foot */
.foot{margin-top:40px;position:relative}
.land{display:block;width:100%;height:90px}
.land .b1{fill:color-mix(in oklab, var(--land) 38%, var(--paper))}
.land .b2{fill:color-mix(in oklab, var(--land) 70%, var(--paper))}
.land .b3{fill:var(--land)}
.foot-in{background:linear-gradient(var(--land), var(--deep));color:#f3ecdc;padding:6px 0 40px}
.foot-in .wrap{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;font-family:var(--f-display);font-weight:600;font-size:13.5px;letter-spacing:.12em;text-transform:uppercase}
.home .foot, .nf .foot{--land:#24525a;--deep:#173a40}

/* narrower screens */
@media (max-width:980px){
  .shelf{grid-template-columns:1fr;gap:20px}
  .course{display:grid;grid-template-columns:minmax(220px, 38%) 1fr}
  .course-link{display:contents}
  .course .art{grid-row:1 / span 2}
  .course-txt{align-self:end;padding:24px 26px 6px}
  .course .jump{align-self:start;padding:12px 26px 24px}
  .hero{grid-template-columns:1fr 280px;gap:26px}
  .hero h1{font-size:58px}
  .psets{grid-template-columns:1fr}
}
@media (max-width:720px){
  body{font-size:16px}
  .wrap{padding:0 16px}
  .top{flex-direction:column;align-items:stretch;gap:12px;padding-top:16px}
  .courses{overflow-x:auto;scrollbar-width:none}
  .courses a{flex:1;text-align:center;padding:8px 10px;font-size:15px}
  .intro{padding:26px 0 24px}
  .intro h1{font-size:46px}
  .lead{font-size:17.5px}
  .shelf{gap:18px}
  .course{display:flex}
  .course-link{display:flex}
  .course .art{aspect-ratio:1 / 1}
  .course-txt{padding:18px 18px 4px;align-self:stretch}
  .course .jump{padding:12px 18px 18px;align-self:stretch}
  .course .art img{object-position:50% 45%}
  .course h2{font-size:30px}
  .hero{grid-template-columns:1fr;gap:20px;padding:14px 0 26px}
  .hero .art{order:-1;max-width:none;aspect-ratio:1 / 1;border-radius:20px}
  .hero .art img{width:100%;height:100%;object-fit:cover;object-position:50% 45%}
  .hero h1{font-size:44px}
  .hero .exam{font-size:17px}
  .sh h2{font-size:32px}
  .book{grid-template-columns:1fr;padding:18px 16px;gap:0}
  .book:has(.cover){grid-template-columns:92px 1fr;column-gap:16px}
  .book:has(.cover) .book-body{display:contents}
  .book:has(.cover) .cover{position:static;width:92px;grid-row:1 / span 3;align-self:start}
  .book:has(.cover) h3, .book:has(.cover) .when, .book:has(.cover) .chips{grid-column:2}
  .book:has(.cover) .rows{grid-column:1 / -1;margin-top:14px}
  .book h3{font-size:24px}
  .row{grid-template-columns:44px 1fr;gap:6px 12px;padding:12px 0}
  .row .num{width:40px;height:40px;font-size:15px;grid-row:1 / span 2;align-self:start}
  .row .acts{justify-content:flex-start;grid-column:2}
  .name{font-size:17.5px}
  .decks{grid-template-columns:1fr 1fr;gap:12px}
  .deck span{font-size:15px;padding:10px 10px 12px;gap:8px;align-items:flex-start}
  .deck i{font-size:12.5px;padding:2px 5px;min-width:26px}
  .pset{padding:14px 14px 16px}
  .set{grid-template-columns:44px 1fr;gap:6px}
  .btn{padding:7px 11px;font-size:14.5px}
  .land{height:56px}
}
@media (max-width:380px){
  .decks{grid-template-columns:1fr}
}
@media (prefers-reduced-motion:reduce){ *{transition:none !important;scroll-behavior:auto !important} }