/* ---------- Fonts (self-hosted, SIL Open Font License; see /assets/fonts) ---------- */
@font-face { font-family: "Literata"; src: url("/assets/fonts/literata.woff2") format("woff2"); font-weight: 200 900; font-style: normal; font-display: swap; }
@font-face { font-family: "Literata"; src: url("/assets/fonts/literata-italic.woff2") format("woff2"); font-weight: 200 900; font-style: italic; font-display: swap; }
@font-face { font-family: "Public Sans"; src: url("/assets/fonts/public-sans.woff2") format("woff2"); font-weight: 100 900; font-style: normal; font-display: swap; }

/* ---------- Tokens ---------- */
:root {
  --paper: #f4f3f8;
  --sheet: #ffffff;
  --ink: #141a33;
  --ink-2: #474c69;
  --ink-3: #6d728c;
  --rule: #d8d9e5;
  --rule-soft: #eaeaf2;
  --teal: #8a5a12;
  --teal-soft: #f5e9d2;
  --mark: #f2c14e;
  --mark-ink: #141a33;
  --red: #b4303f;
  --red-soft: #f8e3e5;
  --focus: #3b5bdb;
  --btn-bg: #141a33;
  --btn-ink: #ffffff;

  --serif: "Literata", Georgia, "Times New Roman", serif;
  --sans: "Public Sans", system-ui, -apple-system, "Segoe UI", sans-serif;

  --s-1: 0.8125rem;   /* 13 */
  --s0: 1rem;         /* 16 */
  --s1: 1.1875rem;    /* 19 */
  --s2: 1.5rem;       /* 24 */
  --s3: 2.25rem;      /* 36 */
  --s4: 3.25rem;      /* 52 */

  --measure: 68ch;
  --page: 72rem;
  --shell: 1560px;
  --side: 228px;
  --topbar: 56px;
  --radius: 6px;
  --radius-lg: 10px;
  --shadow: 0 1px 2px rgb(20 26 51 / 0.05), 0 2px 8px rgb(20 26 51 / 0.05);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #0d1124;
    --sheet: #151a33;
    --ink: #eceaf3;
    --ink-2: #b0b2c8;
    --ink-3: #8c8fa8;
    --rule: #2a2f4d;
    --rule-soft: #1c2140;
    --teal: #e0b45a;
    --teal-soft: #3a2f17;
    --mark: #f2c14e;
    --red: #f0828d;
    --red-soft: #3d1f27;
    --focus: #8ea8ff;
    --btn-bg: #eceaf3;
    --btn-ink: #0d1124;
  }
}
:root[data-theme="dark"] {
  --paper: #0d1124; --sheet: #151a33; --ink: #eceaf3; --ink-2: #b0b2c8; --ink-3: #8c8fa8;
  --rule: #2a2f4d; --rule-soft: #1c2140; --teal: #e0b45a; --teal-soft: #3a2f17; --mark: #f2c14e;
  --red: #f0828d; --red-soft: #3d1f27; --focus: #8ea8ff; --btn-bg: #eceaf3; --btn-ink: #0d1124;
}


/* ---------- Subject colours (sidebar, course cards, course pages, landing page) ---------- */
:root {
  --s-finance: #12936d; --s-math: #3b5bdb; --s-physics: #7c4ddb; --s-chemistry: #e0612a; --s-biology: #3f9b2f;
  --s-taxes: #c98a12; --s-history: #c2364f; --s-statistics: #0b8aa3; --s-economics: #6c7d18;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) { --s-finance: #3cc79c; --s-math: #7f9cff; --s-physics: #a98bff; --s-chemistry: #ff8f5a; --s-biology: #74c95f; --s-taxes: #e6b44a; --s-history: #ff7088; --s-statistics: #3fc3dc; --s-economics: #b2c552; }
}
:root[data-theme="dark"] { --s-finance: #3cc79c; --s-math: #7f9cff; --s-physics: #a98bff; --s-chemistry: #ff8f5a; --s-biology: #74c95f; --s-taxes: #e6b44a; --s-history: #ff7088; --s-statistics: #3fc3dc; --s-economics: #b2c552; }
[data-subject="finance"] { --subj: var(--s-finance); }
[data-subject="math"] { --subj: var(--s-math); }
[data-subject="physics"] { --subj: var(--s-physics); }
[data-subject="chemistry"] { --subj: var(--s-chemistry); }
[data-subject="biology"] { --subj: var(--s-biology); }
[data-subject="taxes"] { --subj: var(--s-taxes); }
[data-subject="history"] { --subj: var(--s-history); }
[data-subject="statistics"] { --subj: var(--s-statistics); }
[data-subject="economics"] { --subj: var(--s-economics); }
.sub-dot { display: inline-block; width: 9px; height: 9px; border-radius: 50%; background: var(--subj, var(--ink-3)); margin: 0 7px 0 4px; vertical-align: 1px; }

/* Course cards and course pages carry their subject's colour */
.path-card[data-subject] { border-top: 5px solid var(--subj); }
[data-subject] > .card-head .ico, .path-card[data-subject] .ico, .path-top[data-subject] .card-head .ico { background: color-mix(in srgb, var(--subj) 14%, transparent); color: var(--subj); }
.subject[data-subject] .subject-head h2 .i { color: var(--subj); }
.subject[data-subject] .subject-head { border-bottom: 3px solid var(--subj); padding-bottom: 6px; }
.path-top[data-subject] { border-left: 5px solid var(--subj); padding-left: 16px; }

/* ---------- Base ---------- */
*, *::before, *::after { box-sizing: border-box; }
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: var(--s0);
  line-height: 1.5;
  overflow-x: hidden;
}
img, svg { max-width: 100%; }
a { color: inherit; text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; border-radius: 3px; }
h1, h2, h3 { font-family: var(--serif); font-weight: 600; line-height: 1.15; margin: 0 0 0.5em; letter-spacing: -0.01em; }
h1 { font-size: clamp(1.75rem, 6vw, 2.25rem); }
h2 { font-size: clamp(1.3rem, 4vw, 1.6rem); }
h3 { font-size: 1.15rem; }
p { margin: 0 0 1em; }
.lede { font-size: 1.0625rem; color: var(--ink-2); max-width: 62ch; }
.muted { color: var(--ink-2); }
.small { font-size: var(--s-1); }
.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.wrap { max-width: var(--page); margin: 0 auto; padding: 0 16px; }
@media (min-width: 720px) { .wrap { padding: 0 24px; } }

/* Icons: stroke SVGs from icons.js, sized to sit beside text. */
.i { width: 1.2em; height: 1.2em; flex: none; vertical-align: -0.22em; }
.ico {
  display: inline-grid; place-items: center; flex: none;
  width: 34px; height: 34px; border-radius: 8px;
  background: var(--teal-soft); color: var(--teal);
}
.ico .i { width: 19px; height: 19px; }
.ico.ink { background: var(--rule-soft); color: var(--ink); }
.ico.lg { width: 42px; height: 42px; border-radius: 10px; }
.ico.lg .i { width: 23px; height: 23px; }

/* The one bold device: a highlighter swipe behind computed results. */
.mark {
  background: linear-gradient(transparent 52%, var(--mark) 52%, var(--mark) 90%, transparent 90%);
  color: var(--mark-ink);
  padding: 0 0.15em;
  box-decoration-break: clone;
  -webkit-box-decoration-break: clone;
}

/* ---------- App shell: top bar, sidebar, main, footer ---------- */
.site-header { background: var(--sheet); border-bottom: 1px solid var(--rule); }
.topbar { display: flex; align-items: center; gap: 16px; min-height: var(--topbar); max-width: var(--shell); margin: 0 auto; padding: 0 16px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-family: var(--serif); font-weight: 700; font-size: 1.15rem; text-decoration: none; letter-spacing: -0.01em; white-space: nowrap; }
.brand-mark { width: 34px; height: 34px; border-radius: 50%; object-fit: cover; border: 1.5px solid var(--rule); background: #fff; flex: none; }

.account-slot { display: flex; gap: 8px; align-items: center; margin-left: auto; }
.account-slot:empty { display: none; }
.account-slot a { display: inline-flex; align-items: center; gap: 6px; text-decoration: none; color: var(--ink-2); font-weight: 500; font-size: 0.9375rem; min-height: 36px; padding: 4px 10px; border-radius: 99px; }
.account-slot a:hover { color: var(--ink); background: var(--rule-soft); }
.account-slot .account-link { color: var(--ink); border: 1px solid var(--rule); padding: 4px 14px 4px 10px; }
.account-slot .account-link:hover { border-color: var(--ink-2); background: transparent; }
@media (max-width: 479px) { .account-slot .admin-link span { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); } }

/* Phones and tablets: the sidebar is a compact icon bar under the top bar. */
.app-nav { background: var(--sheet); border-bottom: 1px solid var(--rule); }
.app-nav ul { list-style: none; margin: 0; padding: 0; }
.nav-main { display: flex; max-width: 40rem; margin: 0 auto !important; padding: 2px 8px !important; }
.nav-main li { flex: 1 1 0; min-width: 0; }
.nav-main a {
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  padding: 7px 2px 6px; border-radius: 8px; text-decoration: none;
  color: var(--ink-2); font-size: 0.6875rem; font-weight: 600; line-height: 1.2; text-align: center;
}
.nav-main a .i { width: 22px; height: 22px; }
.nav-main a:hover { color: var(--ink); background: var(--rule-soft); }
.nav-main a[aria-current="page"] { color: var(--ink); background: var(--teal-soft); box-shadow: inset 0 3px 0 var(--teal); }
.nav-main a[aria-current="page"] .i { color: var(--teal); }
.nav-main .lbl-long { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.nav-main .lbl-short { max-width: 100%; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.nav-paths-box { display: none !important; }

.site-footer { border-top: 1px solid var(--rule); margin-top: 48px; padding: 20px 0 32px; color: var(--ink-2); font-size: var(--s-1); }
.site-footer .wrap { display: flex; gap: 8px 28px; flex-wrap: wrap; align-items: center; }
.site-footer nav { display: flex; gap: 6px 18px; flex-wrap: wrap; }
.site-footer nav a { display: inline-flex; align-items: center; gap: 5px; }
.site-footer .note { flex-basis: 100%; margin: 0; }

@media (min-width: 1024px) {
  body { font-size: 0.9375rem; }
  body.app {
    display: grid;
    grid-template-columns: minmax(0, 1fr) var(--side) minmax(0, calc(var(--shell) - var(--side))) minmax(24px, 1fr);
    grid-template-rows: auto 1fr auto;
    min-height: 100vh;
  }
  body.app > .site-header { grid-column: 1 / -1; grid-row: 1; position: sticky; top: 0; z-index: 30; }
  .topbar { padding: 0 24px 0 18px; }
  body.app > .app-nav { grid-column: 2; grid-row: 2 / 4; background: transparent; border-bottom: 0; border-right: 1px solid var(--rule); }
  body.app > main, body.app > main.wrap { grid-column: 3; grid-row: 2; min-width: 0; max-width: none; margin: 0; padding: 20px 0 0 28px; }
  body.app > .site-footer { grid-column: 3; grid-row: 3; margin-left: 28px; }
  body.app > main .wrap, body.app > .site-footer .wrap { max-width: none; margin: 0; padding-left: 0; padding-right: 0; }

  .nav-inner { position: sticky; top: var(--topbar); max-height: calc(100vh - var(--topbar)); overflow-y: auto; padding: 16px 12px 24px 6px; }
  .nav-main { display: grid; gap: 2px; max-width: none; padding: 0 !important; }
  .nav-main a, .nav-paths a {
    flex-direction: row; gap: 11px; padding: 8px 10px; font-size: 0.9375rem; font-weight: 500; text-align: left; border-radius: 7px;
  }
  .nav-main a .i { width: 20px; height: 20px; }
  .nav-main .lbl-long { position: static; width: auto; height: auto; overflow: visible; clip: auto; white-space: normal; }
  .nav-main .lbl-short { display: none; }
  .nav-main a[aria-current="page"] { color: var(--ink); background: var(--teal-soft); box-shadow: inset 3px 0 0 var(--teal); font-weight: 600; }
  .nav-main a[aria-current="page"] .i { color: var(--teal); }
  .nav-paths-box { display: block !important; }
  .nav-paths-box[hidden] { display: none !important; }
  .nav-head { margin: 22px 10px 6px; font-size: var(--s-1); font-weight: 600; color: var(--ink-3); }
  .nav-paths { display: grid; gap: 1px; }
  .nav-paths a { display: flex; align-items: center; color: var(--ink-2); text-decoration: none; font-size: 0.875rem; line-height: 1.3; }
  .nav-paths a .i { width: 18px; height: 18px; color: var(--subj, var(--ink-3)); }
  .nav-paths a:hover { color: var(--ink); background: var(--rule-soft); }
  .nav-paths a[aria-current] { color: var(--ink); background: color-mix(in srgb, var(--subj, var(--teal)) 13%, transparent); font-weight: 600; box-shadow: inset 3px 0 0 var(--subj, var(--teal)); }
  .nav-paths a[aria-current] .i { color: var(--subj, var(--teal)); }
  .site-footer { margin-top: 40px; }
  .page-head { padding-top: 4px; }

  h1 { font-size: 2rem; }
  h2 { font-size: 1.375rem; }
  h3 { font-size: 1.0625rem; }
  .lede { font-size: 1rem; }
}

/* ---------- Buttons and forms ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 7px;
  min-height: 44px; padding: 9px 16px;
  border-radius: var(--radius); border: 1.5px solid var(--btn-bg);
  background: var(--btn-bg); color: var(--btn-ink);
  font: 600 var(--s0)/1.2 var(--sans); text-decoration: none; cursor: pointer;
}
.btn .i { width: 18px; height: 18px; }
.btn:hover { filter: brightness(1.12); text-decoration: none; }
.btn.secondary { background: var(--sheet); color: var(--ink); border-color: var(--rule); }
.btn.secondary:hover { border-color: var(--ink-2); filter: none; }
.btn.quiet { background: transparent; color: var(--ink); border-color: transparent; padding-left: 10px; padding-right: 10px; }
.btn.quiet:hover { background: var(--rule-soft); filter: none; }
.btn[disabled] { opacity: 0.45; cursor: not-allowed; }
.btn.listening { background: var(--red); border-color: var(--red); color: #fff; }
.btn.sm { min-height: 36px; padding: 5px 11px; font-size: 0.875rem; gap: 6px; }
.btn.sm .i { width: 16px; height: 16px; }
.btn.icon-only { padding-left: 10px; padding-right: 10px; }
@media (min-width: 1024px) {
  .btn { min-height: 38px; padding: 7px 14px; font-size: 0.9375rem; }
  .btn.sm { min-height: 32px; padding: 4px 10px; font-size: 0.8125rem; }
}
.actions { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }

label { display: block; font-weight: 600; margin-bottom: 6px; }
.field { margin-bottom: 16px; }
.field .hint { font-weight: 400; color: var(--ink-2); font-size: var(--s-1); }
input[type="text"], input[type="email"], input[type="date"], input[type="password"], input[type="number"], input[type="search"], select, textarea {
  width: 100%; min-height: 44px; padding: 9px 12px;
  border: 1.5px solid var(--rule); border-radius: var(--radius);
  background: var(--sheet); color: var(--ink); font: var(--s0)/1.4 var(--sans);
}
/* Smaller fields only with a mouse: on iPhone and iPad, text under 16px makes Safari zoom in on focus. */
@media (min-width: 1024px) and (pointer: fine) {
  input[type="text"], input[type="email"], input[type="date"], input[type="password"], input[type="number"], input[type="search"], select, textarea { min-height: 38px; padding: 7px 11px; font-size: 0.9375rem; }
}
textarea { resize: vertical; }
input:focus, select:focus, textarea:focus { outline: none; border-color: var(--focus); box-shadow: 0 0 0 3px color-mix(in srgb, var(--focus) 25%, transparent); }
.check { display: flex; gap: 10px; align-items: flex-start; font-weight: 400; }
.check input { margin-top: 3px; width: 18px; height: 18px; flex: none; }
.status { padding: 10px 14px; border-radius: var(--radius); border-left: 4px solid var(--ink-3); background: var(--sheet); }
.status.ok { border-color: var(--teal); background: var(--teal-soft); }
.status.err { border-color: var(--red); background: var(--red-soft); }
.status > :last-child { margin-bottom: 0; }

/* ---------- Building blocks: cards, tiles, tags, meta ---------- */
.sheet { background-color: var(--sheet); border: 1px solid var(--rule); border-radius: var(--radius-lg); }
.card { background: var(--sheet); border: 1px solid var(--rule); border-radius: var(--radius-lg); padding: 16px; box-shadow: var(--shadow); min-width: 0; }
@media (min-width: 1024px) { .card { padding: 16px 18px; } }
.card > :last-child { margin-bottom: 0; }
.card-head { display: flex; align-items: center; gap: 12px; margin-bottom: 10px; }
.card-head h2, .card-head h3 { margin: 0; }
.card-head .grow { flex: 1; min-width: 0; }
.card h2 { font-size: 1.15rem; }
.card h3 { font-size: 1.0625rem; }
.card-title { font-family: var(--sans); font-size: 0.9375rem !important; font-weight: 700; letter-spacing: 0; margin: 0 0 10px; display: flex; align-items: center; gap: 8px; }
.card-title .i { color: var(--teal); }
a.card { text-decoration: none; display: block; }
a.card:hover { border-color: var(--ink-3); }

/* Graph paper: a quiet dot grid behind worked math. */
.ruled {
  background-image: radial-gradient(circle, var(--rule) 1px, transparent 1.3px);
  background-size: 22px 22px;
  background-position: 11px 11px;
}

.grid { display: grid; gap: 14px; }
.grid > * { min-width: 0; }
@media (min-width: 720px) { .grid.two, .grid.three, .grid.four { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (min-width: 1100px) { .grid.three { grid-template-columns: repeat(3, minmax(0, 1fr)); } .grid.four { grid-template-columns: repeat(4, minmax(0, 1fr)); } }

.tiles { list-style: none; padding: 0; display: grid; gap: 10px; grid-template-columns: repeat(2, minmax(0, 1fr)); margin: 0; }
@media (min-width: 720px) { .tiles { grid-template-columns: repeat(auto-fill, minmax(10.5rem, 1fr)); } }
.tile { display: flex; gap: 10px; align-items: center; padding: 10px 12px; background: var(--sheet); border: 1px solid var(--rule); border-radius: var(--radius-lg); min-width: 0; }
.tile .n { display: block; font-family: var(--serif); font-weight: 600; font-size: 1.2rem; line-height: 1.2; font-variant-numeric: tabular-nums; }
.tile .l { display: block; color: var(--ink-2); font-size: var(--s-1); line-height: 1.3; }
.tile > span:last-child { min-width: 0; }

.tag { display: inline-flex; align-items: center; gap: 4px; font-size: var(--s-1); font-weight: 600; padding: 1px 8px; border-radius: 99px; border: 1px solid var(--rule); color: var(--ink-2); white-space: nowrap; line-height: 1.5; }
.tag .i { width: 13px; height: 13px; }
.tag.live { border-color: var(--teal); color: var(--teal); background: var(--teal-soft); }

.meta { display: flex; flex-wrap: wrap; gap: 4px 14px; margin: 0; padding: 0; list-style: none; color: var(--ink-2); font-size: var(--s-1); font-variant-numeric: tabular-nums; }
.meta > * { display: inline-flex; align-items: center; gap: 5px; }
.meta .i { width: 15px; height: 15px; color: var(--ink-3); }

.crumbs { display: flex; flex-wrap: wrap; align-items: center; gap: 4px; margin: 0 0 6px; font-size: var(--s-1); color: var(--ink-2); }
.crumbs a { text-decoration: none; display: inline-flex; align-items: center; gap: 4px; }
.crumbs a:hover { text-decoration: underline; }
.crumbs .i { width: 14px; height: 14px; color: var(--ink-3); }

.icon-list { list-style: none; padding: 0; margin: 0; display: grid; gap: 8px; }
.icon-list li { display: grid; grid-template-columns: 22px minmax(0, 1fr); gap: 8px; align-items: start; }
.icon-list li > .i { margin-top: 1px; color: var(--teal); width: 19px; height: 19px; }
.icon-list.no li > .i { color: var(--red); }

/* ---------- Sections and page heads ---------- */
.section { padding-top: 32px; }
.section-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 4px 16px; margin-bottom: 14px; }
.section-head h2 { margin: 0; }
.section-head p { margin: 0; }
.page-head { padding: 20px 0 8px; }
.page-head h1 { margin-bottom: 6px; }
.page-head .lede { margin-bottom: 0; }
.head-row { display: grid; gap: 16px; align-items: end; padding: 16px 0 16px; }
@media (min-width: 1024px) { .head-row { grid-template-columns: minmax(0, 1fr) auto; padding-top: 4px; } }
.head-row h1 { margin-bottom: 4px; }
.head-row .lede { margin: 0; }
.rule-list { list-style: none; margin: 0; padding: 0; border-top: 1px solid var(--rule); }
.rule-list > li { border-bottom: 1px solid var(--rule); padding: 14px 0; }
.plain-list { padding-left: 1.2em; margin: 0; }
.plain-list li { margin-bottom: 6px; }

/* ---------- Home ---------- */
.hero { padding-top: 20px; }
@media (min-width: 1024px) { .hero { padding-top: 4px; } .hero .tiles { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
.hero-grid { display: grid; gap: 24px; align-items: stretch; }
@media (min-width: 1024px) { .hero-grid { grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 28px; } }
.hero h1 { font-size: clamp(1.9rem, 6.5vw, 2.6rem); max-width: 18ch; margin-bottom: 12px; }
.hero .lede { font-size: 1.0625rem; }
.hero .actions { margin: 18px 0 20px; }
.hero-copy { display: flex; flex-direction: column; justify-content: center; }
.demo { padding: 20px; }
.demo-head { display: flex; gap: 10px; align-items: center; margin-bottom: 14px; }
.demo-q { font-family: var(--serif); font-size: 1.15rem; margin: 0; }
.demo-controls { display: grid; gap: 12px; grid-template-columns: 1fr; margin-bottom: 14px; }
@media (min-width: 520px) { .demo-controls { grid-template-columns: 1fr 1fr; } }
.demo-controls label { display: flex; justify-content: space-between; font-weight: 500; color: var(--ink-2); margin-bottom: 2px; }
.demo-controls output { color: var(--ink); font-weight: 700; font-variant-numeric: tabular-nums; }
input[type="range"] { width: 100%; accent-color: var(--teal); min-height: 28px; }
.demo-result { font-family: var(--serif); font-size: clamp(1.1rem, 2.4vw, 1.35rem); line-height: 1.6; font-variant-numeric: tabular-nums; margin-bottom: 8px; }
.demo-note { margin: 10px 0 0; color: var(--ink-2); font-size: var(--s-1); }

.how .card-head { margin-bottom: 6px; }
.how p { margin: 0; color: var(--ink-2); }
.how .step-n { font: 600 var(--s-1)/1 var(--sans); color: var(--ink-3); }

.path-card { display: flex; flex-direction: column; gap: 10px; }
.path-card h3 { margin: 0 0 5px; font-size: 1.1rem; }
.path-card h3 a { text-decoration: none; }
.path-card h3 a:hover { text-decoration: underline; }
.path-card .sum { color: var(--ink-2); font-size: 0.9375rem; margin: 0; }
.path-card .foot { margin-top: auto; display: flex; flex-wrap: wrap; gap: 8px; align-items: center; justify-content: space-between; padding-top: 10px; border-top: 1px solid var(--rule-soft); }
.path-card .price-sm { font-family: var(--serif); font-weight: 600; font-size: 1.1rem; }

.cta-band { padding-top: 16px; }
.cta { display: grid; gap: 14px; align-items: center; }
@media (min-width: 900px) { .cta { grid-template-columns: auto minmax(0, 1fr) auto; gap: 18px; } }
.cta h2 { margin: 0 0 4px; }
.cta p { margin: 0; }

/* ---------- Courses ---------- */
.subject { padding-top: 20px; }
.subject-head { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.subject-head h2 { margin: 0; }
.coming-row { display: grid; gap: 10px; }
@media (min-width: 720px) { .coming-row { grid-template-columns: repeat(3, minmax(0, 1fr)); } }
.coming-row .card { display: flex; gap: 12px; align-items: center; box-shadow: none; background: transparent; border-style: dashed; }
.coming-row .card p { margin: 0; }
.stat-rows { display: grid; grid-template-columns: minmax(0, 1fr); gap: 5px; margin: 0; font-size: var(--s-1); }
.stat-rows div { display: flex; gap: 7px; align-items: flex-start; min-width: 0; }
.stat-rows dt { display: contents; }
.stat-rows dd { margin: 0; color: var(--ink-2); }
.stat-rows dd b { color: var(--ink); font-weight: 600; font-variant-numeric: tabular-nums; }
.stat-rows .i { width: 16px; height: 16px; margin-top: 1px; color: var(--teal); }

/* ---------- Path dashboard ---------- */
.path-top { display: grid; gap: 14px; align-items: start; }
@media (min-width: 1100px) { .path-top { grid-template-columns: minmax(0, 1fr) 20rem; gap: 20px; } }
.path-top .tiles { margin-top: 14px; }
.enrol-card .price { font-family: var(--serif); font-size: 2rem; font-weight: 600; line-height: 1.1; margin: 0 0 2px; }
.enrol-card .actions { margin-top: 12px; }
.enrol-card .actions .btn { flex: 1 1 auto; }
.enrol-card .facts { grid-template-columns: minmax(0, 1fr); padding-top: 12px; border-top: 1px solid var(--rule-soft); }
.enrol-card .facts dd, aside.card .facts dd { margin-bottom: 6px; }
.facts { display: grid; gap: 4px 20px; grid-template-columns: max-content 1fr; margin: 12px 0 0; font-size: 0.9375rem; }
.facts dt { color: var(--ink-2); display: flex; align-items: center; gap: 6px; }
.facts dt .i { width: 16px; height: 16px; color: var(--ink-3); }
.facts dd { margin: 0; font-variant-numeric: tabular-nums; }
@media (max-width: 519px) { .facts { grid-template-columns: 1fr; } .facts dd { margin-bottom: 6px; } }
.price { font-family: var(--serif); font-size: var(--s3); font-weight: 600; }

.mod-table { border: 1px solid var(--rule); border-radius: var(--radius-lg); background: var(--sheet); overflow: hidden; box-shadow: var(--shadow); }
.mod-table-head, .mod-row { display: grid; gap: 6px 16px; grid-template-columns: 2rem minmax(0, 1fr); padding: 12px 14px; }
.mod-table-head { display: none; background: var(--rule-soft); font-size: var(--s-1); font-weight: 600; color: var(--ink-2); padding-top: 8px; padding-bottom: 8px; }
.mod-row { border-top: 1px solid var(--rule); align-items: start; }
.mod-row:first-of-type { border-top: 0; }
.mod-row .num { font-family: var(--serif); font-weight: 600; color: var(--ink-3); font-variant-numeric: tabular-nums; font-size: 1.05rem; line-height: 1.4; }
.mod-row .title { font-weight: 700; margin: 0; font-size: 1rem; line-height: 1.4; }
.mod-row .blurb { color: var(--ink-2); font-size: var(--s-1); margin: 2px 0 0; max-width: 90ch; }
.mod-row .stats, .mod-row .go { grid-column: 2; }
.mod-row .stats { display: flex; flex-wrap: wrap; gap: 4px 14px; font-size: var(--s-1); color: var(--ink-2); font-variant-numeric: tabular-nums; }
.mod-row .stats .tag { align-self: flex-start; }
.mod-row .stats span { display: inline-flex; gap: 5px; align-items: center; }
.mod-row .stats .i { width: 15px; height: 15px; color: var(--ink-3); }
.mod-row .go { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.lesson-grid { list-style: none; margin: 8px 0 0; padding: 0; display: grid; gap: 0 18px; grid-template-columns: minmax(0, 1fr); font-size: 0.875rem; }
@media (min-width: 1200px) { .lesson-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
.lesson-grid a { display: grid; grid-template-columns: 1.3rem minmax(0, 1fr) auto; gap: 6px; align-items: baseline; padding: 3px 4px; border-radius: 5px; text-decoration: none; color: var(--ink); }
.lesson-grid a:hover { background: var(--teal-soft); }
.lesson-grid a:hover .t { text-decoration: underline; }
.lesson-grid .n { color: var(--ink-3); font-variant-numeric: tabular-nums; font-size: var(--s-1); text-align: right; }
.lesson-grid .m { color: var(--ink-3); font-size: 0.75rem; font-variant-numeric: tabular-nums; white-space: nowrap; }
.lesson-grid .done .n { color: var(--teal); }
.lesson-grid .done .n .i { width: 14px; height: 14px; vertical-align: -2px; }
.lesson-grid .free { color: var(--teal); font-size: 0.75rem; font-weight: 600; margin-left: 4px; }
@media (min-width: 900px) {
  .mod-table-head, .mod-row { grid-template-columns: 2rem minmax(0, 1fr) 9.5rem 12.5rem; }
  .mod-table-head { display: grid; }
  .mod-row .stats { grid-column: 3; flex-direction: column; gap: 4px; padding-top: 3px; }
  .mod-row .go { grid-column: 4; flex-direction: column; align-items: stretch; }
  .mod-row .go .btn { justify-content: flex-start; }
}

/* ---------- Lecture room ---------- */
.room { display: grid; gap: 20px; padding: 16px 0 0; }
.room > * { min-width: 0; }
@media (min-width: 1024px) { .room { grid-template-columns: minmax(0, 1fr) 19rem; gap: 22px; padding-top: 0; } }
@media (min-width: 1360px) { .room { grid-template-columns: minmax(0, 1fr) 21rem; } }
.lecture-head { display: flex; flex-wrap: wrap; gap: 4px 16px; align-items: baseline; justify-content: space-between; margin-bottom: 10px; }
.lecture-title { margin: 0; font-size: clamp(1.45rem, 5vw, 1.85rem); }
.lecture-head details { font-size: var(--s-1); color: var(--ink-2); flex-basis: 100%; }
.lecture-head details summary { cursor: pointer; display: inline-flex; align-items: center; gap: 4px; }
.lecture-head details ul { margin: 6px 0 0; padding-left: 1.3em; columns: 2 18rem; column-gap: 28px; }

.lesson-rail { display: grid; gap: 14px; align-content: start; }
@media (min-width: 1024px) { .lesson-rail { position: sticky; top: calc(var(--topbar) + 16px); max-height: calc(100vh - var(--topbar) - 32px); overflow-y: auto; } }
.lesson-nav { padding: 14px 10px 10px; }
.lesson-nav .card-head { padding: 0 6px; margin-bottom: 8px; }
.lesson-nav h2 { font: 700 0.9375rem/1.3 var(--sans); letter-spacing: 0; margin: 0; }
.lesson-nav .count { font-size: var(--s-1); color: var(--ink-2); margin: 2px 0 0; }
.lesson-nav .bar { height: 5px; border-radius: 99px; background: var(--rule-soft); overflow: hidden; margin: 8px 6px 8px; }
.lesson-nav .bar span { display: block; height: 100%; background: var(--teal); border-radius: 99px; }
.lesson-nav ol { list-style: none; margin: 0; padding: 0; display: grid; gap: 1px; }
.lesson-nav li a { display: grid; grid-template-columns: 1.4rem minmax(0, 1fr) auto; gap: 6px; align-items: baseline; padding: 6px 8px; border-radius: var(--radius); text-decoration: none; color: var(--ink-2); font-size: 0.875rem; line-height: 1.35; }
.lesson-nav li a .n { color: var(--ink-3); font-variant-numeric: tabular-nums; font-size: var(--s-1); text-align: right; }
.lesson-nav li a .n .i { width: 15px; height: 15px; vertical-align: -3px; }
.lesson-nav li a .m { font-size: 0.75rem; color: var(--ink-3); font-variant-numeric: tabular-nums; }
.lesson-nav li a[aria-current="page"] { background: var(--teal-soft); color: var(--ink); font-weight: 600; box-shadow: inset 3px 0 0 var(--teal); }
.lesson-nav li a[aria-current="page"] .n { color: var(--teal); }
.lesson-nav li a:hover { color: var(--ink); background: var(--rule-soft); }
.lesson-nav .done .n { color: var(--teal); }
.rail-links { display: grid; gap: 2px; padding: 8px; }
.rail-links a { display: flex; gap: 10px; align-items: center; padding: 8px; border-radius: var(--radius); text-decoration: none; font-weight: 500; font-size: 0.9375rem; }
.rail-links a:hover { background: var(--rule-soft); }
.rail-links a[aria-current="page"] { background: var(--teal-soft); font-weight: 600; }
.rail-links a .i { color: var(--teal); }
.rail-links a .sub { margin-left: auto; color: var(--ink-3); font-size: var(--s-1); font-variant-numeric: tabular-nums; }

.board { position: relative; min-height: 20rem; padding: 22px 18px 26px; overflow-x: auto; }
@media (min-width: 720px) { .board { padding: 28px 36px; min-height: 24rem; } }
.board > * + * { margin-top: 18px; }
.board > :first-child { margin-top: 0; }
.board .b-heading { font-family: var(--serif); font-size: clamp(1.25rem, 2.6vw, 1.6rem); font-weight: 600; margin-bottom: 0; }
.board .b-note { font-size: var(--s1); color: var(--ink-2); max-width: 52ch; margin-bottom: 0; }
.board .b-formula { font-family: var(--serif); font-size: clamp(1.2rem, 2.8vw, 1.65rem); font-style: italic; margin-bottom: 0; }
.board .b-plug { font-family: var(--serif); font-size: clamp(1.05rem, 2.2vw, 1.25rem); font-variant-numeric: tabular-nums; margin-bottom: 0; }
.board .b-plug b { color: var(--mark-ink); font-weight: 700; background: linear-gradient(transparent 52%, var(--mark) 52%, var(--mark) 90%, transparent 90%); padding: 0 0.15em; }
.board .b-list { font-family: var(--serif); font-size: var(--s1); padding-left: 1.2em; margin-bottom: 0; }
.board .b-list li { margin-bottom: 6px; }
.board table { background: var(--sheet); border-collapse: collapse; font-variant-numeric: tabular-nums; min-width: 18rem; }
.board caption { text-align: left; font-weight: 600; padding-bottom: 8px; color: var(--ink-2); }
.board th, .board td { padding: 6px 16px 6px 0; text-align: right; border-bottom: 1px solid var(--rule); }
.board th:first-child, .board td:first-child { text-align: left; }
.board th { font-weight: 600; color: var(--ink-2); font-size: var(--s-1); }
.board .b-timeline { width: 100%; max-width: 40rem; height: auto; display: block; }
.board .appear { animation: appear 420ms ease-out both; }
.board .b-code { margin: 0 0 14px; padding: 12px 14px; border-radius: var(--radius); background: var(--rule-soft); overflow-x: auto; font: 0.9rem/1.5 ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace; white-space: pre; }
.board .b-table td:first-child { white-space: pre-wrap; }
@keyframes appear { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) { .board .appear, .appear { animation: none !important; } }

.caption-bar { margin: 12px 0 0; min-height: 4.6em; font-family: var(--serif); font-size: 1.0625rem; line-height: 1.55; max-width: 72ch; }
@media (min-width: 1024px) { .caption-bar { font-size: 1.1rem; } }
.caption-bar .who { font-family: var(--sans); font-weight: 700; font-size: var(--s-1); color: var(--ink-2); display: flex; align-items: center; gap: 5px; }
.caption-bar .who .i { width: 15px; height: 15px; color: var(--teal); }
.controls { display: flex; flex-wrap: wrap; gap: 6px 8px; align-items: center; margin-top: 10px; padding: 8px; border: 1px solid var(--rule); border-radius: var(--radius-lg); background: var(--sheet); }
.controls .progress { margin-left: auto; color: var(--ink-2); font-size: var(--s-1); font-variant-numeric: tabular-nums; padding-right: 6px; }
.controls select { width: auto; min-height: 36px; padding: 4px 8px; }
.controls .sep { width: 1px; align-self: stretch; background: var(--rule); margin: 2px 2px; }
@media (max-width: 719px) { .controls .sep { display: none; } }
.controls .btn.quiet { padding-left: 8px; padding-right: 8px; }
.controls .voice-picker select { max-width: 12.5rem; }
.controls .voice-picker label, .controls .speed-label { font-size: 0.875rem; }
.speed-label { font-weight: 500; color: var(--ink-2); margin: 0; display: inline-flex; gap: 6px; align-items: center; }
.speed-label .i { width: 17px; height: 17px; }

.checkpoint { margin-top: 14px; padding: 16px 18px; border: 1.5px solid var(--ink); border-radius: var(--radius-lg); background: var(--sheet); }
.checkpoint h3 { font-family: var(--sans); font-size: var(--s0); margin-bottom: 6px; color: var(--ink-2); display: flex; align-items: center; gap: 7px; }
.checkpoint h3 .i { color: var(--teal); }
.checkpoint .q { font-family: var(--serif); font-size: var(--s1); }
.checkpoint .options { display: grid; gap: 8px; margin: 12px 0; }
@media (min-width: 900px) { .checkpoint .options { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
.checkpoint .options .btn { justify-content: flex-start; text-align: left; }
.answer-row { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 12px; }
.answer-row input { flex: 1 1 12rem; width: auto; font-variant-numeric: tabular-nums; }
.feedback { margin-top: 12px; }

.ask-panel { margin-top: 16px; }
.ask-panel h2 { font-size: 1.15rem; display: flex; align-items: center; gap: 8px; }
.ask-panel h2 .i { color: var(--teal); }
.thread { display: grid; gap: 10px; margin-bottom: 12px; }
.thread:empty { display: none; }
.msg { max-width: 72ch; padding: 10px 14px; border-radius: var(--radius-lg); line-height: 1.5; }
.msg.student { justify-self: end; background: var(--rule-soft); }
.msg.tutor { background: var(--sheet); border: 1px solid var(--rule); font-family: var(--serif); font-size: 1.04rem; }
.msg.tutor .who, .msg.student .who { display: block; font: 700 var(--s-1)/1.4 var(--sans); color: var(--ink-2); margin-bottom: 2px; }
.msg.thinking { color: var(--ink-2); font-style: italic; }
.msg .cite { font: 600 0.7em/1 var(--sans); color: var(--teal); margin-left: 1px; }
.msg .sources { display: block; margin-top: 10px; padding-top: 8px; border-top: 1px solid var(--rule-soft); font: 400 var(--s-1)/1.5 var(--sans); color: var(--ink-2); }
.msg .sources .source { display: block; }
.msg .sources .cite { margin-right: 4px; }
.ask-form { display: flex; gap: 8px; flex-wrap: wrap; }
.ask-form input { flex: 1 1 14rem; width: auto; }
.voice-note { font-size: var(--s-1); color: var(--ink-2); margin: 8px 0 0; }
.ask-bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.ask-bar .ask-form { flex: 1 1 20rem; }

/* ---------- Practice ---------- */
.practice-grid { display: grid; gap: 18px; padding-top: 4px; }
@media (min-width: 980px) { .practice-grid { grid-template-columns: minmax(0, 1fr) 20rem; gap: 22px; align-items: start; } }
.problem { padding: 20px 18px; }
@media (min-width: 720px) { .problem { padding: 24px 28px; } }
.problem .topic { color: var(--ink-2); font-weight: 600; margin-bottom: 8px; display: flex; align-items: center; gap: 7px; font-size: 0.875rem; }
.problem .topic .i { color: var(--teal); }
.problem .prompt { font-family: var(--serif); font-size: clamp(1.1rem, 2.2vw, 1.3rem); line-height: 1.55; max-width: 70ch; }
.solution { margin-top: 16px; font-family: var(--serif); font-variant-numeric: tabular-nums; }
.solution ol { padding-left: 1.3em; }
.mastery h2 { font-size: 1rem; font-family: var(--sans); letter-spacing: 0; display: flex; align-items: center; gap: 8px; margin-bottom: 10px; }
.mastery h2 .i { color: var(--teal); }
.mastery ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.mastery .bar { height: 6px; border-radius: 99px; background: var(--rule-soft); overflow: hidden; margin-top: 3px; }
.mastery .bar span { display: block; height: 100%; background: var(--teal); border-radius: 99px; transition: width 300ms ease; }
@media (prefers-reduced-motion: reduce) { .mastery .bar span { transition: none; } }
.mastery .row { display: flex; justify-content: space-between; gap: 8px; font-size: var(--s-1); }
.mastery .row b { font-weight: 600; }
.score { margin-top: 14px; color: var(--ink-2); font-size: var(--s-1); }

/* ---------- Prose pages ---------- */
.prose { max-width: var(--measure); }
.prose h2 { font-size: 1.3rem; margin-top: 1.6em; }
.prose li { margin-bottom: 6px; }
.prose-card { padding: 22px 18px; margin-top: 8px; }
@media (min-width: 720px) { .prose-card { padding: 28px 36px; } }
.prose-card > :first-child { margin-top: 0; }
.legal-grid { display: grid; gap: 18px; align-items: start; }
@media (min-width: 1100px) { .legal-grid { grid-template-columns: minmax(0, 48rem) 17rem; gap: 24px; } }
.legal-grid .prose-card { max-width: none; }
.legal-grid .prose-card > * { max-width: var(--measure); }
.legal-grid aside { display: grid; gap: 12px; }
@media (min-width: 1100px) { .legal-grid aside { position: sticky; top: calc(var(--topbar) + 16px); } }
.form-card { padding: 20px 18px; max-width: 36rem; }
@media (min-width: 720px) { .form-card { padding: 24px 26px; } }
.hp { position: absolute; left: -9999px; }
.split-aside { display: grid; gap: 18px; align-items: start; }
@media (min-width: 1024px) { .split-aside { grid-template-columns: minmax(0, 36rem) minmax(0, 24rem); gap: 24px; } }
.split-aside .form-card { max-width: none; }

/* Dark mode: a half-height swipe leaves dark digits on a dark page, so use a full marker block. */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .mark,
  :root:not([data-theme="light"]) .board .b-plug b { background: var(--mark); border-radius: 3px; }
}
:root[data-theme="dark"] .mark,
:root[data-theme="dark"] .board .b-plug b { background: var(--mark); border-radius: 3px; }

/* ---------- Accounts, payments and admin ---------- */
.provider-list { display: grid; gap: 10px; margin: 8px 0 18px; }
.provider-btn { display: flex; align-items: center; justify-content: center; gap: 10px; min-height: 46px; border: 1px solid var(--rule); border-radius: var(--radius); background: var(--sheet); color: var(--ink); font-weight: 600; text-decoration: none; }
.provider-btn:hover { border-color: var(--ink-2); text-decoration: none; }
.provider-btn .glyph { display: inline-grid; place-items: center; width: 22px; height: 22px; border-radius: 4px; font-size: 0.8rem; font-weight: 800; color: #fff; }
.glyph.google { background: #3b6fd8; } .glyph.microsoft { background: #3c7a3c; } .glyph.yahoo { background: #6a2fbe; } .glyph.apple { background: #1d1d1f; }

.enrolled-list { list-style: none; padding: 0; margin: 0 0 14px; display: grid; gap: 10px; }
.enrolled-list li { display: flex; flex-wrap: wrap; gap: 10px 16px; align-items: center; justify-content: space-between; }
.enrolled-list li .who { display: flex; gap: 12px; align-items: center; }

.account-grid { display: grid; gap: 18px; align-items: start; }
@media (min-width: 1024px) { .account-grid { grid-template-columns: minmax(0, 1fr) 22rem; gap: 22px; } }
.account-grid > * { min-width: 0; }

.stat-grid { display: grid; gap: 10px; grid-template-columns: repeat(auto-fill, minmax(min(9.5rem, calc(50% - 5px)), 1fr)); margin: 0 0 8px; }
.stat { display: flex; gap: 10px; align-items: center; background: var(--sheet); border: 1px solid var(--rule); border-radius: var(--radius-lg); padding: 10px 12px; }
.stat .n { display: block; font-family: var(--serif); font-size: 1.25rem; font-weight: 600; font-variant-numeric: tabular-nums; line-height: 1.2; }
.stat .l { display: block; color: var(--ink-2); font-size: var(--s-1); line-height: 1.3; }

.checklist { list-style: none; padding: 0; margin: 0; display: grid; gap: 8px; }
.checklist li { display: grid; grid-template-columns: 1.5rem minmax(0, 1fr); gap: 8px; align-items: start; }
.checklist .ok, .checklist .todo { display: inline-grid; place-items: center; }
.checklist .ok { color: var(--teal); }
.checklist .todo { color: var(--ink-3); }
.checklist .i { width: 19px; height: 19px; margin-top: 1px; }

.table-wrap { position: relative; overflow-x: auto; border: 1px solid var(--rule); border-radius: var(--radius-lg); background: var(--sheet); }
.data-table { width: 100%; border-collapse: collapse; font-size: 0.875rem; }
.data-table th, .data-table td { text-align: left; padding: 8px 12px; border-bottom: 1px solid var(--rule-soft); vertical-align: top; }
.data-table th { font-weight: 600; color: var(--ink-2); font-size: var(--s-1); background: var(--rule-soft); white-space: nowrap; }
.data-table tr:last-child td { border-bottom: none; }
.data-table .num { text-align: right; font-variant-numeric: tabular-nums; }
.inline-form { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.inline-form select, .inline-form input { width: auto; min-width: 9rem; }
.price-grid { display: grid; gap: 12px 16px; grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr)); margin-bottom: 14px; }
.admin-section { padding-top: 24px; }
.admin-section h2, #content h2 { font-size: 1.2rem; display: flex; align-items: center; gap: 8px; }
.admin-section h2 .i, #content h2 .i { color: var(--teal); }
.admin-top { display: grid; gap: 18px; }
@media (min-width: 1100px) { .admin-top { grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 22px; } }
.admin-top > * { min-width: 0; }
.admin-top .admin-section { padding-top: 16px; }

/* ---------- Office hours ---------- */
.office { display: grid; gap: 18px; align-items: start; }
@media (min-width: 1024px) { .office { grid-template-columns: minmax(0, 1fr) 21rem; gap: 22px; } }
.office > * { min-width: 0; }
.office-main { margin-top: 0; display: flex; flex-direction: column; min-height: 22rem; }
@media (min-width: 1024px) { .office-main { min-height: calc(100vh - var(--topbar) - 220px); } }
.office-main .thread { flex: 1; align-content: start; }
.office-side { display: grid; gap: 14px; }
.suggest { display: grid; gap: 6px; }
.suggest .btn { justify-content: flex-start; text-align: left; font-weight: 500; line-height: 1.35; padding-top: 6px; padding-bottom: 6px; }

/* Admin: free access by email */
.free-grid { display: grid; grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr); gap: 16px; align-items: start; }
@media (max-width: 720px) { .free-grid { grid-template-columns: 1fr; } }
.free-grid textarea { width: 100%; }
.link-btn { border: 0; background: none; padding: 0 0 0 4px; cursor: pointer; color: inherit; display: inline-flex; align-items: center; vertical-align: middle; }
.link-btn svg { width: 14px; height: 14px; }
.link-btn:hover, .link-btn:focus-visible { color: var(--red); }
.status-text.ok { color: var(--teal); }
.status-text.err { color: var(--red); }

/* Subjects and levels (home and courses) */
.chip { display: inline-flex; align-items: center; gap: 4px; min-height: 30px; font: inherit; font-size: var(--s-1); padding: 4px 11px; border-radius: 99px; border: 1.5px solid var(--rule); background: var(--sheet); color: var(--ink); cursor: pointer; }
.chip[aria-pressed="true"] { background: var(--ink); color: var(--sheet); border-color: var(--ink); }
.chip:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }
.level-filter { display: flex; flex-wrap: wrap; gap: 6px; }
.subjects-head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: flex-end; gap: 10px 20px; }
.subject-card { display: flex; flex-direction: column; gap: 10px; }
.subject-card h3 { margin: 0 0 5px; font-size: 1.15rem; }
.subject-card h3 a { text-decoration: none; }
.subject-card h3 a:hover { text-decoration: underline; }
.subject-card .sum { color: var(--ink-2); font-size: 0.9375rem; margin: 0; }
.subject-card .foot { margin-top: auto; }
.subject-card.coming { opacity: 0.8; }
.level-tags { display: inline-flex; flex-wrap: wrap; gap: 4px; }
.path-mini { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; }
.path-mini li { display: flex; justify-content: space-between; gap: 8px; flex-wrap: wrap; border-top: 1px solid var(--rule); padding-top: 4px; }
.path-mini a { font-weight: 600; text-decoration: none; }
.path-mini a:hover { text-decoration: underline; }
.filter-bar { display: flex; flex-wrap: wrap; gap: 10px 24px; align-items: center; margin: 4px 0 18px; }
.filter-bar .lbl { font-size: var(--s-1); color: var(--ink-2); margin-right: 4px; }
.level-head { display: flex; align-items: baseline; gap: 10px; margin: 18px 0 10px; }
.level-head h3 { margin: 0; font-size: 1rem; }

/* Touch screens (iPhone, iPad): every control is comfortably tappable. */
@media (pointer: coarse) {
  .btn.sm, .chip { min-height: 40px; }
  .chip { padding: 6px 13px; }
  .problem-list a, .path-mini a, .lesson-rail a { min-height: 40px; }
  .link-btn { min-width: 32px; min-height: 32px; justify-content: center; }
  .crumbs a { display: inline-flex; align-items: center; min-height: 32px; }
  input, select, textarea { font-size: max(16px, 1rem); }
}
/* iPhone home indicator and rounded corners when the page is added to the home screen. */
@supports (padding: env(safe-area-inset-bottom)) {
  .site-footer { padding-bottom: max(16px, env(safe-area-inset-bottom)); }
}

/* ---------- Dialogs (human tutoring request form) ---------- */
.modal { border: 1px solid var(--rule); border-radius: var(--radius-lg); padding: 0; width: min(560px, calc(100vw - 32px)); max-height: calc(100vh - 32px); background: var(--sheet); color: var(--ink); box-shadow: 0 18px 48px rgb(21 35 63 / 0.25); }
.modal::backdrop { background: rgb(20 26 51 / 0.5); }
.modal .modal-body { padding: 20px 22px; overflow: auto; max-height: calc(100vh - 34px); }
.modal .modal-head { display: flex; align-items: center; gap: 10px; justify-content: space-between; margin-bottom: 8px; }
.modal .modal-head h2 { margin: 0; font-size: var(--s1); }
.modal .field { margin-bottom: 12px; }
.modal .two { display: grid; gap: 12px; grid-template-columns: 1fr; }
@media (min-width: 520px) { .modal .two { grid-template-columns: 1fr 1fr; } }
.req-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.req-list > li { border: 1px solid var(--rule); border-radius: var(--radius); padding: 12px 14px; background: var(--sheet); }
.req-list .req-head { display: flex; flex-wrap: wrap; gap: 8px; align-items: baseline; justify-content: space-between; }
.req-list .req-desc { white-space: pre-wrap; margin: 6px 0; }
.req-status { font-size: var(--s-1); font-weight: 600; padding: 2px 8px; border-radius: 999px; background: var(--rule-soft); color: var(--ink-2); }
.req-status.new { background: color-mix(in srgb, var(--mark) 45%, var(--sheet)); color: var(--mark-ink); }
.req-status.contacted { background: var(--teal-soft); color: var(--teal); }
.req-status.closed { background: var(--rule-soft); color: var(--ink-3); }

/* ---------- Menu badges ---------- */
.nav-main a { position: relative; }
.nav-badge { display: inline-grid; place-items: center; min-width: 18px; height: 18px; padding: 0 5px; border-radius: 999px; background: var(--red); color: #fff; font-size: 11px; font-weight: 700; line-height: 1; margin-left: auto; }
@media (max-width: 1023px) { .nav-badge { position: absolute; top: 2px; right: 18%; } }

/* ---------- Live tutoring ---------- */
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chips .chip { cursor: default; }
.chip-x { border: 0; background: none; padding: 0 0 0 2px; cursor: pointer; color: var(--ink-2); display: inline-grid; }
.chip-x .i { width: 14px; height: 14px; }
.tutor-card .tutor-bio { white-space: pre-wrap; display: -webkit-box; -webkit-line-clamp: 5; -webkit-box-orient: vertical; overflow: hidden; }
.msg-list { list-style: none; margin: 8px 0 0; padding: 8px 10px; border-left: 3px solid var(--rule); background: var(--paper); border-radius: 4px; display: grid; gap: 6px; font-size: var(--s-1); white-space: pre-wrap; }
.rate-row { border: 0; padding: 0; margin: 0 0 10px; display: flex; flex-wrap: wrap; align-items: center; gap: 6px 10px; }
.rate-row legend { font-weight: 600; font-size: var(--s-1); margin-bottom: 4px; width: 100%; }
.rate-row label { display: inline-flex; align-items: center; gap: 4px; cursor: pointer; }
.slot-rows { display: grid; gap: 8px; }
.slot-rows .inline-form input[type="datetime-local"] { min-width: 13rem; }
.req-status.requested, .req-status.slot_chosen, .req-status.times_offered { background: color-mix(in srgb, var(--mark) 45%, var(--sheet)); color: var(--mark-ink); }
.req-status.confirmed, .req-status.completed { background: var(--teal-soft); color: var(--teal); }
.req-status.declined, .req-status.cancelled { background: var(--rule-soft); color: var(--ink-3); }

/* ---------- Admin: model order and log screens ---------- */
.model-rows { margin: 0; padding-left: 1.4rem; display: grid; gap: 6px; }
.model-rows li { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 4px 6px; align-items: center; }
.model-rows select, .model-rows input[type="text"] { width: 100%; min-width: 0; }
.model-rows [data-ms] { grid-column: 1 / -1; margin-top: -2px; }
.model-rows [data-ms]:empty { display: none; }
.modal.modal-wide { width: min(1400px, calc(100vw - 24px)); height: calc(100vh - 24px); max-height: none; }
.modal.modal-wide .modal-body { max-height: calc(100vh - 26px); }
.log-table { max-height: calc(100vh - 190px); overflow: auto; }
.log-table thead th { position: sticky; top: 0; background: var(--sheet); z-index: 1; }
.log-table td { vertical-align: top; font-size: var(--s-1); }
.log-table td:nth-child(4) { min-width: 18rem; }
.log-table pre { white-space: pre-wrap; word-break: break-word; max-width: 60rem; margin: 6px 0 0; }
.log-table tr.lvl-error td:nth-child(2) { color: var(--red); font-weight: 600; }
.log-table tr.lvl-warn td:nth-child(2) { color: #8a5a00; font-weight: 600; }
button.sort { all: unset; cursor: pointer; font-weight: 600; white-space: nowrap; }
button.sort:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

/* ---------- Math: formulas, worked steps, graphs, figures, number lines ---------- */
.tex-display { margin: 0.4em 0; overflow-x: auto; overflow-y: hidden; }
.katex { font-size: 1.12em; }
.board .b-math { margin-bottom: 0; }
.board .b-math-tex { font-size: clamp(1.15rem, 2.6vw, 1.5rem); overflow-x: auto; overflow-y: hidden; padding: 2px 0; }
.board .b-math-tex .katex-display { margin: 0.2em 0; text-align: left; }
.board .b-math-tex .katex-display > .katex { text-align: left; }
.board .b-math.hl .b-math-tex { background: linear-gradient(transparent 8%, color-mix(in srgb, var(--mark) 45%, transparent) 8%, color-mix(in srgb, var(--mark) 45%, transparent) 92%, transparent 92%); display: inline-block; padding: 2px 10px; border-radius: 4px; }
.board .b-math-cap { font-size: var(--s-1); color: var(--ink-3); margin: 4px 0 0; }
.board .b-steps { display: grid; gap: 8px; font-size: clamp(1.05rem, 2.2vw, 1.25rem); }
.board .b-step { display: flex; flex-wrap: wrap; align-items: baseline; gap: 6px 22px; }
.board .b-step-tex { min-width: 12ch; }
.board .b-step-why { font-size: var(--s-1); color: var(--ink-3); }
/* ---------- Chemistry: molecules, reactions, mechanisms, Newman projections, chairs, spectra, energy levels (chemboard.js) ---------- */
.b-chem { margin: 0; color: var(--ink); --el-O: #c8323c; --el-N: #2f5bd8; --el-S: #a07800; --el-P: #c46a00; --el-F: #2c8a3e; --el-Cl: #2c8a3e; --el-Br: #8a3a1e; --el-I: #6a2b8a; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .b-chem { --el-O: #ff7b85; --el-N: #8ea8ff; --el-S: #f0c74e; --el-P: #ffad5c; --el-F: #7ad98d; --el-Cl: #7ad98d; --el-Br: #e39272; --el-I: #c79bea; } }
:root[data-theme="dark"] .b-chem { --el-O: #ff7b85; --el-N: #8ea8ff; --el-S: #f0c74e; --el-P: #ffad5c; --el-F: #7ad98d; --el-Cl: #7ad98d; --el-Br: #e39272; --el-I: #c79bea; }
.b-chem figcaption { font-size: var(--s-1); color: var(--ink-2); margin-top: 4px; }
.chem-row { display: flex; flex-wrap: wrap; align-items: center; gap: 6px 10px; min-height: 40px; }
.mol-part { display: inline-flex; flex-direction: column; align-items: center; max-width: 100%; }
.mol-name { font-size: var(--s-1); color: var(--ink-2); text-align: center; }
.mol-wait { font-family: var(--mono, monospace); font-size: var(--s-1); color: var(--ink-3); padding: 8px; }
.b-chem svg { max-width: 100%; height: auto; display: block; overflow: visible; font-family: var(--sans); }
.b-chem svg line, .b-chem svg .ringb { stroke: currentColor; stroke-width: 1.6; stroke-linecap: round; }
.b-chem svg .wedge { fill: currentColor; }
.b-chem svg .hash { stroke-width: 1.2; }
.b-chem svg text { fill: currentColor; font-size: 14px; }
.b-chem svg .atom { font-weight: 600; }
.b-chem svg .el-O { fill: var(--el-O); } .b-chem svg .el-N { fill: var(--el-N); } .b-chem svg .el-S { fill: var(--el-S); } .b-chem svg .el-P { fill: var(--el-P); }
.b-chem svg .el-F, .b-chem svg .el-Cl { fill: var(--el-F); } .b-chem svg .el-Br { fill: var(--el-Br); } .b-chem svg .el-I { fill: var(--el-I); }
.b-chem svg .lblbg { fill: var(--sheet); }
.b-chem svg .chg { font-size: 12px; font-weight: 700; }
.b-chem svg .dot, .b-chem svg .dotc { fill: currentColor; }
.b-chem svg .note { font-size: 12px; fill: var(--teal); font-style: italic; }
.b-chem svg .hl { fill: color-mix(in srgb, var(--mark) 55%, transparent); stroke: none; }
.b-chem svg .hl-bond { stroke: color-mix(in srgb, var(--mark) 70%, transparent); stroke-width: 9; }
.b-chem svg .arrow .curve { fill: none; stroke: var(--red); stroke-width: 1.6; }
.b-chem svg .arrow .head { fill: var(--red); stroke: none; }
.b-chem svg .arrow .barb { fill: none; stroke: var(--red); stroke-width: 1.6; }
.b-chem svg .arrow { opacity: 0; animation: chem-in 0.45s ease-out forwards; animation-delay: calc(var(--i, 0) * 0.6s + 0.3s); }
@keyframes chem-in { to { opacity: 1; } }
@media (prefers-reduced-motion: reduce) { .b-chem svg .arrow { animation: none; opacity: 1; } }
.rx-plus { font-size: 1.4rem; color: var(--ink-2); }
.rx-arrow { display: inline-grid; grid-template-rows: auto auto auto; justify-items: center; min-width: 74px; font-size: var(--s-1); color: var(--ink-2); }
.rx-glyph { font-size: 1.7rem; line-height: 1; color: var(--ink); }
.rx-above, .rx-below { min-height: 1em; text-align: center; max-width: 12rem; }
.rx-text { font-size: 0.95rem; }
.b-newman svg, .b-chair svg { max-width: 260px; }
.b-newman svg .ring { fill: var(--sheet); stroke: currentColor; stroke-width: 1.6; }
.b-newman svg .grp, .b-chair svg .grp { font-size: 13px; font-weight: 600; }
.b-chair svg .num { font-size: 10px; fill: var(--ink-3); }
.b-chair svg .axial { stroke: var(--focus); } .b-chair svg .equatorial { stroke: var(--teal); }
.b-spectrum, .b-energylevels { max-width: 600px; }
.b-chem svg.spectrum .ax, .b-chem svg.spectrum .tk { stroke: var(--ink-2); stroke-width: 1.2; }
.b-chem svg.spectrum .tkl { font-size: 11px; fill: var(--ink-3); }
.b-chem svg .unit { font-size: 11.5px; fill: var(--ink-2); }
.b-chem svg.spectrum .pk { stroke: var(--focus); stroke-width: 1.6; }
.b-chem svg.spectrum .trace { fill: none; stroke: var(--focus); stroke-width: 1.5; }
.b-chem svg.spectrum .plab, .b-chem svg.spectrum .intg { font-size: 11.5px; font-weight: 600; }
.b-chem svg.spectrum .intg { fill: var(--teal); }
.b-chem svg.energy .lvl { stroke: currentColor; stroke-width: 2.2; }
.b-chem svg.energy .e { fill: none; stroke: var(--red); stroke-width: 1.6; }
.b-chem svg.energy .link { stroke: var(--ink-3); stroke-width: 1; stroke-dasharray: 3 3; }
.b-chem svg.energy .eax { stroke: var(--ink-3); stroke-width: 1.2; } .b-chem svg.energy .head { fill: var(--ink-3); }
.b-chem svg.energy .llab { font-size: 12px; } .b-chem svg.energy .ctitle { font-size: 12px; fill: var(--ink-2); font-weight: 600; }
.b-figure { max-width: 520px; }
.b-figure svg { width: 100%; height: auto; display: block; color: var(--ink); font-family: var(--sans); font-size: 13px; }
.b-figure .grid line { stroke: var(--rule-soft); stroke-width: 1; }
.b-figure .axes line { stroke: var(--ink-2); stroke-width: 1.4; }
.b-figure .axes text { fill: var(--ink-3); font-size: 11.5px; }
.b-figure text.lbl:not([fill]) { fill: var(--ink); }
.b-figure text.lbl { font-size: 13.5px; font-weight: 600; paint-order: stroke; stroke: var(--sheet); stroke-width: 3.5px; stroke-linejoin: round; }
.b-figure text.pt { font-style: italic; font-family: var(--serif); font-size: 15px; }
.b-figure .draw { stroke-dasharray: 1; stroke-dashoffset: 1; animation: draw-in 1.6s ease-out forwards; }
@keyframes draw-in { to { stroke-dashoffset: 0; } }
@media (prefers-reduced-motion: reduce) { .b-figure .draw { animation: none; stroke-dashoffset: 0; stroke-dasharray: none; } }
.math-input { font-family: var(--serif); font-size: var(--s1); }
.math-preview { min-height: 1.8em; color: var(--ink-2); font-size: var(--s1); margin-top: 6px; }
.math-keys { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; }
.math-keys button { min-width: 40px; padding: 6px 10px; border: 1px solid var(--rule); border-radius: var(--radius); background: var(--sheet); color: var(--ink); font-family: var(--serif); font-size: var(--s0); cursor: pointer; }
.math-keys button:hover { border-color: var(--ink-3); }

/* ---------- Talking with the tutor (live spoken conversation) ---------- */
.talk-panel { position: fixed; z-index: 60; right: 16px; bottom: 16px; width: min(420px, calc(100vw - 32px)); max-height: min(560px, calc(100vh - 32px)); display: flex; flex-direction: column; background: var(--sheet); color: var(--ink); border: 1px solid var(--rule); border-radius: var(--radius-lg); box-shadow: 0 12px 40px rgb(21 35 63 / 0.22); }
.talk-panel[hidden] { display: none; }
.talk-head { display: flex; align-items: center; gap: 10px; padding: 12px 14px; border-bottom: 1px solid var(--rule-soft); }
.talk-head > div { flex: 1; display: flex; flex-direction: column; line-height: 1.25; }
.talk-state { font-size: var(--s-1); color: var(--ink-3); }
.talk-dot { width: 12px; height: 12px; border-radius: 50%; background: var(--ink-3); flex: none; }
.talk-panel[data-state="listening"] .talk-dot, .talk-panel[data-state="hearing"] .talk-dot { background: var(--red); animation: talk-pulse 1.2s ease-in-out infinite; }
.talk-panel[data-state="thinking"] .talk-dot { background: var(--mark); animation: talk-pulse 0.8s ease-in-out infinite; }
.talk-panel[data-state="speaking"] .talk-dot { background: var(--teal); animation: talk-pulse 1.6s ease-in-out infinite; }
@keyframes talk-pulse { 50% { transform: scale(1.35); opacity: 0.6; } }
@media (prefers-reduced-motion: reduce) { .talk-dot { animation: none !important; } }
.talk-log { flex: 1; overflow-y: auto; padding: 12px 14px; display: flex; flex-direction: column; gap: 10px; min-height: 140px; }
.talk-log .msg { margin: 0; }
.talk-log .msg.interim { opacity: 0.65; font-style: italic; }
.talk-note { margin: 0; padding: 0 14px 8px; }
.talk-controls { display: flex; gap: 8px; align-items: center; padding: 10px 14px 14px; border-top: 1px solid var(--rule-soft); }
.talk-type { flex: 1; display: flex; gap: 6px; min-width: 0; }
.talk-type input { flex: 1; min-width: 0; }
@media (max-width: 560px) { .talk-panel { right: 8px; left: 8px; bottom: 8px; width: auto; max-height: 70vh; } }
.p-board { min-height: 0; padding: 12px 0 0; }
.q-board { margin: 14px 0; }
.q-board:empty, .q-board[hidden] { display: none; }
.checkpoint .q-show { font-size: var(--s1); margin: 4px 0 10px; }
.nav-sub { list-style: none; }
.nav-sub summary { cursor: pointer; padding: 6px 10px; font-size: 0.875rem; font-weight: 600; color: var(--ink-2); border-radius: var(--radius); list-style-position: inside; }
.nav-sub summary:hover { background: var(--rule-soft); color: var(--ink); }
.nav-sub .nav-paths { margin: 2px 0 6px 8px; }
.talk-setup { margin: 0 14px 8px; padding: 10px 12px; border-radius: var(--radius); background: var(--teal-soft); color: var(--ink); }
.talk-setup p { margin: 0; }
.talk-setup-actions { display: flex; gap: 8px; margin-top: 8px; }
.talk-setup-actions[hidden] { display: none; }
.nowrap { white-space: nowrap; }