/* the subjects page (/subjects/) and the units on a subject's page */
.subhead { display: flex; justify-content: space-between; align-items: flex-end; gap: 16px; flex-wrap: wrap; margin: 40px 0 28px; }
.subhead h1 { margin: 0; }
.seg { display: inline-flex; padding: 3px; border-radius: 999px; background: var(--card); box-shadow: var(--lift); }
.seg button { border: 0; background: none; cursor: pointer; padding: 9px 16px; border-radius: 999px; font: 500 12px var(--mono); letter-spacing: .04em; color: var(--muted); }
.seg button[aria-pressed="true"] { background: var(--hi); color: #fff; }
.v-chapters { display: none; }
html[data-view="chapters"] .v-subjects { display: none; }
html[data-view="chapters"] .v-chapters { display: block; }

.subjects { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 340px), 1fr)); gap: 22px; }
.subject { display: flex; flex-direction: column; background: var(--card); box-shadow: var(--lift); border-radius: 16px; overflow: hidden; text-decoration: none; color: var(--text);
  transition: transform .5s cubic-bezier(.16,1,.3,1); }
@media (hover: hover) { a.subject:hover { transform: translateY(-4px); } }
.subject img { width: 100%; height: auto; aspect-ratio: 16 / 10; object-fit: cover; display: block; }
.subject .body { padding: 18px 22px 22px; }
.subject h2 { font: 400 34px/1 var(--serif); color: var(--strong); margin: 0 0 6px; }
.subject .sub { font: italic 19px var(--serif); color: var(--muted); }
.subject ul { list-style: none; padding: 0; margin: 14px 0 0; display: grid; gap: 4px; font-size: 14px; }
.subject ul span { font: 12px var(--mono); color: var(--muted); } .subject ul span::before { content: '· '; }
.subject.soon { box-shadow: none; border: 1px dashed var(--faint); background: transparent; justify-content: center; padding: 28px 22px; align-self: start; }
.subject.soon h2 { color: var(--lo); font-size: 26px; } .subject.soon .sub { color: var(--faint); }

.unit-list { margin: 0 0 36px; }
.unit-list h2 { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; font: 400 26px var(--serif); color: var(--strong); margin: 0 0 12px; }
.unit-list h2 a { text-decoration: none; } .unit-list h2 small { font: 500 11px var(--mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.unit-list h3 { font: 500 12px var(--mono); letter-spacing: .1em; text-transform: uppercase; color: var(--muted); margin: 18px 0 8px; }
.chaps { list-style: none; padding: 0; display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 260px), 1fr)); gap: 8px; }
.chaps a { display: grid; grid-template-columns: 48px 1fr; align-items: center; gap: 12px; padding: 8px 10px 8px 8px; border-radius: 10px; background: var(--card);
  border: 1px solid var(--faint); text-decoration: none; color: var(--text); }
.chaps a:hover { border-color: var(--mid); }
.chaps img { width: 48px; height: 43px; object-fit: cover; border-radius: 6px; }
.chaps b { display: block; font: 400 19px/1.1 var(--serif); color: var(--strong); }
.chaps span { font: 11px var(--mono); color: var(--muted); }

/* a subject's own page: its units, each a clearly separate shelf */
.unit { max-width: 1180px; margin: 64px auto 18px; padding: 0 4px; display: flex; align-items: baseline; gap: 14px; flex-wrap: wrap; border-top: 1px solid var(--faint); padding-top: 22px; }
.unit .no { font: 500 12px var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--muted); }
.unit h2 { font: 400 clamp(28px, 3.4vw, 40px)/1.05 var(--serif); color: var(--strong); margin: 0; }
.unit .count { margin-left: auto; font: 500 12px var(--mono); color: var(--muted); }
.crumbs { width: 100%; max-width: 1180px; margin: 6px auto 0; padding: 0; display: flex; gap: 14px; font: 500 12px var(--mono); letter-spacing: .06em; text-transform: uppercase; color: var(--muted); }
.crumbs a { color: var(--muted); text-decoration: none; } .crumbs a:hover { color: var(--strong); }
/* a subject's equation sheet: a pill under the hero's subtext */
.hero .pill { display: inline-block; margin-top: 22px; padding: 10px 18px; border: 1px solid var(--faint); border-radius: 999px; background: var(--card);
  font: 500 12px var(--mono); letter-spacing: .06em; text-transform: uppercase; color: var(--hi); text-decoration: none; }
.hero .pill:hover { border-color: var(--mid); color: var(--strong); }

/* a subject's own page: the chapter list, as wide as the page's shelves were */
.subject-list { max-width: 1180px; margin: 8px auto 0; padding: 0 4px; }
.subject-list h3 { font: 400 clamp(24px, 2.6vw, 30px)/1.1 var(--serif); letter-spacing: 0; text-transform: none; color: var(--strong); margin: 40px 0 12px; }
.subject-list h3:first-child { margin-top: 8px; }

/* phones: full-width view toggle, a shorter picture, each unit a row with its count on the right; the subject page's
   chapters as one list per unit */
@media (max-width: 600px) {
  .subhead { display: block; margin: 18px 0 20px; }
  .subhead h1 { font-size: 40px; margin-bottom: 14px; }
  .seg { display: grid; grid-template-columns: 1fr 1fr; }
  .seg button { padding: 11px 0; }
  .subjects { gap: 14px; }
  .subject img { aspect-ratio: 2 / 1; }
  .subject .body { padding: 14px 16px 6px; }
  .subject h2 { font-size: 30px; margin-bottom: 2px; }
  .subject .sub { font-size: 17px; }
  .subject ul { gap: 0; margin-top: 10px; }
  .subject li { display: flex; justify-content: space-between; align-items: center; gap: 12px; padding: 11px 0; border-top: 1px solid var(--faint); color: var(--strong); line-height: 1.35; }
  .subject ul span { white-space: nowrap; } .subject ul span::before { content: none; }
  .subject.soon { flex-direction: row; align-items: baseline; gap: 10px; padding: 16px; }
  .subject.soon h2 { font-size: 22px; margin: 0; }

  .crumbs { margin-top: 6px; padding: 0; gap: 8px; font-size: 11px; white-space: nowrap; }
  .hero { text-align: left; margin: 18px 0 8px; }
  .hero h1 { font-size: 40px; }
  .hero p { font-size: 17px; margin-top: 8px; }
  .hero .pill { margin-top: 14px; padding: 9px 14px; font-size: 11px; }
  .subject-list { padding: 0; }
  .unit-list h3, .subject-list h3 { margin: 26px 0 10px; }
  .subject-list h3:first-child { margin-top: 0; }
  .chaps { gap: 0; background: var(--card); border-radius: 14px; box-shadow: var(--lift); overflow: hidden; }
  .chaps li + li { border-top: 1px solid var(--faint); }
  .chaps a { grid-template-columns: 64px 1fr auto; padding: 8px 14px 8px 8px; border: 0; border-radius: 0; background: none; }
  .chaps a::after { content: '›'; font: 20px var(--serif); color: var(--lo); }
  .chaps img { width: 64px; height: 52px; border-radius: 8px; }
}