/* COMS 6998 AI-Native Computing — site styles.
   Light and dark are both first-class: tokens on :root, overridden by
   [data-theme="dark"] and by prefers-color-scheme when no explicit choice. */

:root {
  --bg: #fbfbf8;
  --panel: #ffffff;
  --panel-2: #f4f4ef;
  --text: #191c22;
  --muted: #5a6372;
  --line: #e6e5dd;
  --line-soft: #eeede6;

  --comp: #0072ce;            /* Computing for AI — Columbia blue */
  --comp-ink: #005ba6;
  --comp-soft: rgba(0, 114, 206, 0.09);
  --ai: #6c4ec9;              /* AI for Computing — violet */
  --ai-ink: #5b3fb4;
  --ai-soft: rgba(108, 78, 201, 0.09);

  --amber-ink: #8a4a03;
  --amber-soft: #fdf0d3;
  --tbd-ink: #8a4a03;
  --tbd-soft: #fdf0d3;

  --shadow: 0 1px 2px rgba(20, 24, 34, 0.05), 0 8px 24px -18px rgba(20, 24, 34, 0.25);
  --radius: 14px;
  --radius-sm: 8px;

  --sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Helvetica, Arial, sans-serif;
  --serif: "Source Serif 4", Georgia, "Times New Roman", serif;
}

[data-theme="dark"] { color-scheme: dark; }
:root:not([data-theme]) { color-scheme: light dark; }

[data-theme="dark"] {
  --bg: #0e1116;
  --panel: #151a22;
  --panel-2: #1a202a;
  --text: #e7eaf0;
  --muted: #9aa4b4;
  --line: #262d39;
  --line-soft: #1f2530;

  --comp: #5aa9f5;
  --comp-ink: #7ebcf8;
  --comp-soft: rgba(90, 169, 245, 0.12);
  --ai: #a78bfa;
  --ai-ink: #bda5fb;
  --ai-soft: rgba(167, 139, 250, 0.13);

  --amber-ink: #f3c355;
  --amber-soft: rgba(243, 195, 85, 0.13);
  --tbd-ink: #f3c355;
  --tbd-soft: rgba(243, 195, 85, 0.12);

  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 10px 28px -20px rgba(0, 0, 0, 0.7);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]):not([data-theme="dark"]) {
    --bg: #0e1116;
    --panel: #151a22;
    --panel-2: #1a202a;
    --text: #e7eaf0;
    --muted: #9aa4b4;
    --line: #262d39;
    --line-soft: #1f2530;
    --comp: #5aa9f5;
    --comp-ink: #7ebcf8;
    --comp-soft: rgba(90, 169, 245, 0.12);
    --ai: #a78bfa;
    --ai-ink: #bda5fb;
    --ai-soft: rgba(167, 139, 250, 0.13);
    --amber-ink: #f3c355;
    --amber-soft: rgba(243, 195, 85, 0.13);
    --tbd-ink: #f3c355;
    --tbd-soft: rgba(243, 195, 85, 0.12);
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 10px 28px -20px rgba(0, 0, 0, 0.7);
  }
}

/* ---------------------------------------------------------------- base */

* { box-sizing: border-box; }

[hidden] { display: none !important; }

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0, 0, 0, 0);
  white-space: nowrap; border: 0;
}

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.wrap { max-width: 1060px; margin: 0 auto; padding: 0 24px; }

a { color: var(--comp-ink); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 2px; }

h1, h2, h3 { line-height: 1.2; letter-spacing: -0.015em; margin: 0 0 0.5rem; }
h2 { font-size: 1.7rem; font-weight: 750; }
h3 { font-size: 1.05rem; font-weight: 650; }

code { font-size: 0.9em; background: var(--panel-2); padding: 0.1em 0.35em; border-radius: 5px; }

time { font-variant-numeric: tabular-nums; }

.skip-link {
  position: absolute; left: -9999px; top: 0;
  background: var(--panel); color: var(--text); padding: 8px 14px; z-index: 100;
  border-radius: 0 0 var(--radius-sm) 0;
}
.skip-link:focus { left: 0; }

:focus-visible { outline: 2px solid var(--comp); outline-offset: 2px; border-radius: 3px; }

.tbd {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 650;
  letter-spacing: 0.06em;
  color: var(--tbd-ink);
  background: var(--tbd-soft);
  border: 1px dashed color-mix(in srgb, var(--tbd-ink) 45%, transparent);
  border-radius: 6px;
  padding: 0 6px;
  vertical-align: 1px;
}

.pending { color: var(--muted); font-size: 0.85em; font-style: italic; }

.fine { color: var(--muted); font-size: 0.86rem; margin-bottom: 0; }

/* ---------------------------------------------------------------- header */

.site-head {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line-soft);
}

.site-head nav {
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; height: 58px;
}

.brand { display: flex; align-items: center; gap: 10px; color: var(--text); font-size: 0.95rem; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.brand strong { font-weight: 750; }
.brand-sub { color: var(--muted); font-weight: 450; }
.brand-mark {
  display: inline-grid; place-items: center;
  width: 26px; height: 26px; border-radius: 8px;
  font-size: 0.95rem; font-weight: 700; color: #fff;
  background: linear-gradient(120deg, #0072ce, #6c4ec9);
}

.nav-links { display: flex; align-items: center; gap: 4px; }
.nav-links a {
  color: var(--muted); font-size: 0.9rem; font-weight: 550;
  padding: 6px 10px; border-radius: 8px;
}
.nav-links a:hover { color: var(--text); background: var(--panel-2); text-decoration: none; }
.nav-links a.active { color: var(--text); background: var(--panel-2); }

#theme-toggle {
  margin-left: 6px;
  border: 1px solid var(--line); background: var(--panel);
  color: var(--text); border-radius: 999px;
  width: 34px; height: 34px; cursor: pointer;
  display: inline-grid; place-items: center; font-size: 0.9rem; line-height: 1;
}
#theme-toggle:hover { background: var(--panel-2); }
:root:not([data-theme="dark"]) #theme-toggle .ico-sun { display: none; }
[data-theme="dark"] #theme-toggle .ico-moon { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]):not([data-theme="dark"]) #theme-toggle .ico-sun { display: inline; }
  :root:not([data-theme="light"]):not([data-theme="dark"]) #theme-toggle .ico-moon { display: none; }
}

/* ---------------------------------------------------------------- hero */

.hero { padding: 64px 0 24px; }

.hero-grid {
  display: grid; grid-template-columns: 1fr 280px;
  gap: 40px; align-items: start;
}

.eyebrow {
  margin: 0 0 10px;
  font-size: 0.8rem; font-weight: 650; letter-spacing: 0.14em;
  text-transform: uppercase; color: var(--muted);
}

.hero h1 {
  font-size: clamp(2.3rem, 5.5vw, 3.4rem);
  font-weight: 800; letter-spacing: -0.03em; margin-bottom: 6px;
}

.duality-line {
  margin: 0 0 20px;
  font-size: clamp(1.05rem, 2.4vw, 1.35rem);
  font-weight: 650; letter-spacing: -0.01em;
}
.duality-line .d-comp { color: var(--comp-ink); }
.duality-line .d-ai { color: var(--ai-ink); }
.duality-line .d-arrows { color: var(--muted); font-weight: 450; padding: 0 8px; }

.thesis {
  margin: 0 0 22px;
  padding-left: 18px;
  border-left: 3px solid transparent;
  border-image: linear-gradient(to bottom, var(--comp), var(--ai)) 1;
  font-family: var(--serif);
  font-style: italic;
  font-size: 1.12rem;
  line-height: 1.65;
  color: color-mix(in srgb, var(--text) 88%, var(--muted));
  max-width: 58ch;
}

.meta-chips { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 8px; }
.meta-chips li {
  font-size: 0.85rem; font-weight: 550; color: var(--muted);
  background: var(--panel); border: 1px solid var(--line);
  border-radius: 999px; padding: 5px 13px;
}

.instructor-card {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 20px 22px;
  box-shadow: var(--shadow);
}
.card-kicker {
  margin: 0 0 4px; font-size: 0.72rem; font-weight: 700;
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--muted);
}
.inst-name { margin: 0 0 10px; font-size: 1.15rem; font-weight: 700; }
.inst-links { list-style: none; margin: 0 0 14px; padding: 0; font-size: 0.9rem; }
.inst-links li { padding: 2px 0; }
.tbd-list {
  list-style: none; margin: 0; padding: 12px 0 0;
  border-top: 1px solid var(--line-soft);
  font-size: 0.85rem; color: var(--muted);
}
.tbd-list li { display: flex; justify-content: space-between; align-items: center; gap: 10px; padding: 3px 0; }
.oh { color: var(--text); font-weight: 550; text-align: right; font-size: 0.85rem; }

.duality-panel {
  margin-top: 44px;
  display: grid; grid-template-columns: 1fr 1fr; gap: 16px;
}
.d-card {
  border-radius: var(--radius); padding: 20px 22px;
  border: 1px solid var(--line); background: var(--panel);
}
.d-card h2 { font-size: 1.02rem; margin-bottom: 6px; }
.d-card p { margin: 0; color: var(--muted); font-size: 0.92rem; }
.d-dir { font-weight: 450; margin-right: 4px; }
.d-card-comp { border-top: 3px solid var(--comp); }
.d-card-comp h2 { color: var(--comp-ink); }
.d-card-ai { border-top: 3px solid var(--ai); text-align: right; }
.d-card-ai h2 { color: var(--ai-ink); }
.d-shared {
  grid-column: 1 / -1;
  font-size: 0.9rem; color: var(--muted);
  background: var(--panel-2); border-radius: var(--radius-sm);
  padding: 12px 18px; text-align: center;
}
.d-shared strong { color: var(--text); font-weight: 650; }

/* ---------------------------------------------------------------- sections */

.section { padding: 40px 0; }
.section + .section { border-top: 1px solid var(--line-soft); }

.section-head {
  display: flex; flex-wrap: wrap; align-items: baseline;
  justify-content: space-between; gap: 12px;
}

.section-lede { color: var(--muted); max-width: 72ch; margin: 4px 0 26px; }

.panel {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 20px 22px;
  margin-bottom: 16px;
}
.panel > :last-child { margin-bottom: 0; }
.panel > h2, .track h2 {
  font-size: 1.05rem; font-weight: 650; letter-spacing: -0.015em;
}

.col2 { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; align-items: stretch; }
.col2 .panel { margin-bottom: 0; }
.col2 { margin-bottom: 16px; }

/* ---------------------------------------------------------------- now / announcements */

.now-section { padding: 12px 0 42px; }
.now-heading {
  display: flex; align-items: baseline; gap: 12px;
  margin-bottom: 14px;
}
.now-heading .eyebrow { margin: 0; color: var(--comp-ink); }
.now-heading h2 { font-size: 1.15rem; margin: 0; }
.now-grid {
  display: grid; grid-template-columns: 1.35fr 0.72fr 1.1fr;
  gap: 14px;
}
.now-panel {
  min-width: 0; background: var(--panel);
  border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px 18px;
}
.now-class-panel { border-top: 3px solid var(--comp); }
.now-deadline-panel { border-top: 3px solid var(--amber-ink); }
.now-news-panel { border-top: 3px solid var(--ai); }
.now-label, .now-kicker, .now-subhead {
  margin: 0 0 7px; color: var(--muted);
  font-size: 0.7rem; font-weight: 700;
  letter-spacing: 0.1em; text-transform: uppercase;
}
.now-class h3 { font-size: 1rem; margin-bottom: 10px; }
.now-class h3 a { color: var(--text); }
.now-state { color: var(--comp-ink); }
.now-readings { margin: 0; padding-left: 20px; font-size: 0.84rem; }
.now-readings li { padding: 2px 0; }
.now-readings a { color: var(--text); font-weight: 580; }
.now-readings .venue { font-size: 0.68rem; }
.now-deadline-item time {
  display: block; color: var(--amber-ink);
  font-size: 0.82rem; font-weight: 700;
}
.now-deadline-item p { margin: 4px 0 0; font-size: 0.94rem; font-weight: 650; }
.now-empty { margin: 0; color: var(--muted); font-size: 0.86rem; }
.now-news { list-style: none; margin: 0; padding: 0; }
.now-news li {
  display: grid; grid-template-columns: 48px 1fr; gap: 10px;
  padding: 8px 0; border-bottom: 1px solid var(--line-soft);
}
.now-news li:first-child { padding-top: 0; }
.now-news li:last-child { padding-bottom: 0; border-bottom: 0; }
.now-news time { color: var(--muted); font-size: 0.74rem; font-weight: 650; }
.now-news strong { display: block; font-size: 0.84rem; }
.now-news p { margin: 1px 0 0; color: var(--muted); font-size: 0.78rem; line-height: 1.45; }

/* ---------------------------------------------------------------- page titles & at-a-glance */

.page-title { font-size: 1.9rem; font-weight: 800; letter-spacing: -0.02em; margin-bottom: 0.4rem; }

.ext { font-size: 0.72em; margin-left: 2px; opacity: 0.7; }

.table-scroll {
  overflow-x: auto;
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
}
.glance-table { width: 100%; border-collapse: collapse; font-size: 0.92rem; }
.glance-table th {
  text-align: left; font-size: 0.72rem; font-weight: 700;
  letter-spacing: 0.1em; text-transform: uppercase; color: var(--muted);
  padding: 12px 14px 8px; border-bottom: 1px solid var(--line);
}
.glance-table td {
  padding: 9px 14px; border-bottom: 1px solid var(--line-soft);
  vertical-align: baseline;
}
.glance-table tbody tr:last-child td { border-bottom: none; }
.glance-table td:nth-child(1) {
  font-weight: 700; font-variant-numeric: tabular-nums;
  color: var(--muted); width: 1%;
}
.glance-table td:nth-child(2) { white-space: nowrap; color: var(--muted); font-size: 0.86rem; font-weight: 600; width: 1%; }
.glance-table td:nth-child(3) { font-weight: 600; }
.glance-table td:nth-child(3) a { color: var(--text); }
.glance-table td:nth-child(3) a:hover { color: var(--comp-ink); }
.glance-table .g-dl { color: var(--amber-ink); font-size: 0.85rem; width: 32%; }
.glance-table .g-holiday td { color: var(--muted); font-style: italic; }
.glance-table .g-module td {
  padding: 7px 14px; font-size: 0.72rem; font-weight: 750;
  letter-spacing: 0.1em; text-transform: uppercase;
}
.g-module.m-comp td { color: var(--comp-ink); background: var(--comp-soft); }
.g-module.m-ai td { color: var(--ai-ink); background: var(--ai-soft); }
.g-dot { margin-right: 9px; vertical-align: 1px; }
.g-dot.m-comp { background: var(--comp); }
.g-dot.m-ai { background: var(--ai); }
.g-dot.m-span { background: linear-gradient(135deg, var(--comp), var(--ai)); }
.g-dot.m-proj { background: var(--muted); }

/* ---------------------------------------------------------------- what you'll learn + prerequisites */

#learn { padding-top: 0; border-top: none; }
.learn-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 14px; }
.learn-card {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 16px 20px;
}
.learn-card p { margin: 0; font-size: 0.92rem; color: var(--muted); line-height: 1.65; }
.learn-card strong { color: var(--text); font-weight: 680; }

.prereq-panel { margin-bottom: 0; }
.prereq-list { margin: 0 0 14px; }
.prereq-list > div {
  display: grid; grid-template-columns: 190px 1fr; gap: 6px 20px;
  padding: 10px 0; border-bottom: 1px solid var(--line-soft);
}
.prereq-list > div:first-child { padding-top: 0; }
.prereq-list > div:last-child { border-bottom: none; }
.prereq-list dt { font-weight: 680; font-size: 0.92rem; }
.prereq-list dd { margin: 0; font-size: 0.92rem; color: var(--muted); line-height: 1.65; }

/* ---------------------------------------------------------------- students */

.students-grid {
  list-style: none; margin: 0; padding: 0;
  display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 16px;
}
.stu-card {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 20px 12px 16px;
  display: flex; flex-direction: column; align-items: center; gap: 10px;
  text-align: center;
}
.stu-photo {
  width: 72px; height: 72px; border-radius: 50%;
  object-fit: cover; display: block;
}
.stu-initials {
  display: grid; place-items: center;
  background: linear-gradient(135deg, var(--comp-soft), var(--ai-soft));
  color: var(--text); font-weight: 700; font-size: 1.25rem;
}
.stu-name { font-weight: 600; font-size: 0.92rem; }
.stu-name a { color: var(--text); }
.stu-name a:hover { color: var(--comp-ink); }
.roster-empty p { margin: 0; color: var(--muted); }

/* ---------------------------------------------------------------- schedule */

.sched-tools { display: flex; align-items: center; flex-wrap: wrap; gap: 14px; font-size: 0.84rem; }
.legend { display: inline-flex; align-items: center; gap: 6px; color: var(--muted); font-weight: 550; }
.dot { width: 9px; height: 9px; border-radius: 50%; display: inline-block; }
.dot-comp { background: var(--comp); }
.dot-ai { background: var(--ai); }

#toggle-optionals {
  border: 1px solid var(--line); background: var(--panel); color: var(--muted);
  font: inherit; font-size: 0.8rem; font-weight: 550;
  border-radius: 999px; padding: 4px 12px; cursor: pointer;
}
#toggle-optionals:hover { color: var(--text); background: var(--panel-2); }
.tool-link { font-weight: 600; }

/* quick navigation: weeks grouped by module */
.sched-toc {
  display: grid; grid-template-columns: 1fr 1.15fr 1.15fr;
  gap: 16px 28px; margin: 0 0 28px; padding: 18px 22px;
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
}
.toc-col { display: flex; flex-direction: column; }
.toc-col-edge { justify-content: space-between; gap: 16px; }
.toc-group ol { list-style: none; margin: 0; padding: 0; }
.toc-head {
  margin: 0 0 6px; font-size: 0.72rem; font-weight: 750;
  letter-spacing: 0.1em; text-transform: uppercase;
  padding-bottom: 5px; border-bottom: 2px solid var(--line);
}
.toc-head.m-comp { color: var(--comp-ink); border-bottom-color: var(--comp); }
.toc-head.m-ai { color: var(--ai-ink); border-bottom-color: var(--ai); }
.toc-head.m-span {
  color: var(--muted);
  border-image: linear-gradient(90deg, var(--comp), var(--ai)) 1;
}
.toc-group li a {
  display: flex; gap: 8px; align-items: baseline;
  padding: 3px 4px; margin: 0 -4px; border-radius: 6px;
  font-size: 0.85rem; font-weight: 550; color: var(--text); line-height: 1.4;
}
.toc-group li a:hover { background: var(--panel-2); color: var(--comp-ink); text-decoration: none; }
.toc-num { color: var(--muted); font-weight: 700; font-size: 0.76rem; font-variant-numeric: tabular-nums; }

/* module divider rows in the week list */
.module-divider {
  display: flex; align-items: center; gap: 14px;
  margin: 20px 0 2px; font-size: 0.82rem; font-weight: 750;
  letter-spacing: 0.1em; text-transform: uppercase;
}
.module-divider, .week { scroll-margin-top: 76px; }
.module-divider::after { content: ""; flex: 1; border-bottom: 2px solid; opacity: 0.3; }
.module-divider.m-comp { color: var(--comp-ink); }
.module-divider.m-comp::after { border-color: var(--comp); }
.module-divider.m-ai { color: var(--ai-ink); }
.module-divider.m-ai::after { border-color: var(--ai); }

.weeks { display: flex; flex-direction: column; gap: 14px; }
.weeks .module-divider:first-child { margin-top: 0; }

.week {
  position: relative;
  display: grid; grid-template-columns: 96px 1fr; gap: 20px;
  background: var(--panel); border: 1px solid var(--line);
  border-left-width: 3px;
  border-radius: var(--radius);
  padding: 18px 22px 18px 18px;
  box-shadow: var(--shadow);
}
.week.m-comp { border-left-color: var(--comp); }
.week.m-ai { border-left-color: var(--ai); }
.week.m-proj { border-left-color: var(--muted); }
.week.m-span, .policy-ai, .papers-week.m-span {
  border-left: 3px solid transparent;
  background:
    linear-gradient(var(--panel), var(--panel)) padding-box,
    linear-gradient(to bottom, var(--comp), var(--ai)) border-box;
}
.t-loop {
  border-top: 3px solid transparent;
  background:
    linear-gradient(var(--panel), var(--panel)) padding-box,
    linear-gradient(90deg, var(--comp), var(--ai)) border-box;
}

.week.past { opacity: 0.62; }
.week.past:hover, .week.past:focus-within { opacity: 1; }
.week.current {
  border-color: color-mix(in srgb, var(--comp) 55%, var(--line));
  box-shadow: 0 0 0 3px var(--comp-soft), var(--shadow);
}

.week-rail { display: flex; flex-direction: column; gap: 2px; padding-top: 3px; }
.wk-num {
  font-size: 1.5rem; font-weight: 800; letter-spacing: -0.02em;
  color: color-mix(in srgb, var(--text) 82%, var(--muted));
  font-variant-numeric: tabular-nums; line-height: 1.1;
}
.wk-date { color: var(--muted); font-size: 0.85rem; font-weight: 600; white-space: nowrap; }

.week-body { min-width: 0; }

.week-tags { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 8px; }

.chip {
  display: inline-flex; align-items: center;
  font-size: 0.72rem; font-weight: 650; letter-spacing: 0.03em;
  border-radius: 999px; padding: 2px 10px;
  border: 1px solid transparent;
}
.chip-mod { background: var(--panel-2); color: var(--muted); }
.m-comp .chip-mod { background: var(--comp-soft); color: var(--comp-ink); }
.m-ai .chip-mod { background: var(--ai-soft); color: var(--ai-ink); }
.m-span .chip-mod {
  background: linear-gradient(100deg, var(--comp-soft), var(--ai-soft));
  color: var(--text);
}
.chip-guest { background: transparent; border-color: var(--line); color: var(--muted); }
.chip-now { background: var(--comp); color: #fff; }
[data-theme="dark"] .chip-now { color: #0e1116; }
.chip-coled { background: var(--panel-2); color: var(--muted); font-weight: 550; }

.week-title { font-size: 1.18rem; font-weight: 700; margin: 0 0 6px; }
.holiday-title { font-size: 1rem; font-weight: 600; color: var(--muted); margin: 0; align-self: center; }

.week.m-holiday {
  border-style: dashed; border-left-width: 1px; box-shadow: none;
  background: transparent; padding-top: 12px; padding-bottom: 12px;
}
.week.m-holiday .wk-num { font-size: 1rem; font-weight: 500; color: var(--muted); }

.week-note { margin: 0 0 6px; font-size: 0.9rem; color: var(--muted); }
.week-note strong { color: var(--text); font-weight: 620; }

.p-label {
  margin: 12px 0 6px;
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--muted);
}

.papers { list-style: none; margin: 0; padding: 0; counter-reset: paper; }
.papers li {
  counter-increment: paper;
  position: relative;
  padding: 7px 0 7px 26px;
  border-bottom: 1px solid var(--line-soft);
}
.papers li:last-child { border-bottom: none; }
.papers li::before {
  content: counter(paper);
  position: absolute; left: 0; top: 10px;
  width: 17px; height: 17px;
  font-size: 0.68rem; font-weight: 700;
  display: grid; place-items: center;
  border-radius: 5px;
  background: var(--panel-2); color: var(--muted);
}

.p-head { display: inline; }
.p-title { font-weight: 600; font-size: 0.96rem; }
.p-title a { color: var(--text); }
.p-title a:hover { color: var(--comp-ink); }
.venue {
  display: inline-block; margin-left: 8px;
  font-size: 0.74rem; font-weight: 650; color: var(--muted);
  background: var(--panel-2); border-radius: 5px; padding: 1px 7px;
  white-space: nowrap; vertical-align: 1px;
}
.p-extra { font-size: 0.8rem; font-weight: 600; margin-left: 8px; white-space: nowrap; }
.p-extra::before { content: "↗ "; font-size: 0.75em; }
.focus { display: block; font-size: 0.85rem; color: var(--muted); margin-top: 2px; }

.optional { margin-top: 10px; }
.optional summary {
  cursor: pointer; font-size: 0.84rem; font-weight: 600; color: var(--muted);
  list-style: none; display: inline-flex; align-items: center; gap: 6px;
  border-radius: 6px; padding: 2px 4px;
}
.optional summary::-webkit-details-marker { display: none; }
.optional summary::before { content: "▸"; font-size: 0.8em; transition: transform 0.15s; }
.optional[open] summary::before { transform: rotate(90deg); }
.optional summary:hover { color: var(--text); }
.opt-count { font-weight: 450; }
.optional-list {
  margin: 8px 0 0; padding-left: 34px;
  font-size: 0.86rem; color: var(--muted); line-height: 1.55;
}
.optional-list li { padding: 3px 0; }
.optional-list a { color: var(--muted); }
.optional-list a:hover { color: var(--text); }
.papers-optional { margin: 2px 0 16px; padding-left: 22px; }

.deadlines { list-style: none; margin: 12px 0 0; padding: 0; display: flex; flex-wrap: wrap; gap: 6px; }
.deadlines li {
  font-size: 0.8rem; font-weight: 600;
  color: var(--amber-ink); background: var(--amber-soft);
  border-radius: 7px; padding: 3px 10px;
}
.deadlines li::before { content: "⏱ "; opacity: 0.75; }

.registrar-line { margin: 22px 0 0; font-size: 0.84rem; color: var(--muted); }

/* ---------------------------------------------------------------- format */

.time-table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
.time-table td, .time-table th { padding: 6px 0; border-bottom: 1px solid var(--line-soft); vertical-align: top; }
.time-table th { text-align: left; }
.time-table tr:last-child td, .time-table tr:last-child th { border-bottom: none; }
.time-table th:first-child {
  white-space: nowrap; padding-right: 16px; width: 1%;
  font-variant-numeric: tabular-nums; font-weight: 600; color: var(--muted);
  font-size: 0.84rem;
}

.lead-panel { margin-bottom: 16px; }
.lead-blocks { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 12px; margin-bottom: 12px; }
.lead-block {
  background: var(--panel-2); border-radius: var(--radius-sm);
  padding: 12px 14px; font-size: 0.86rem; color: var(--muted);
}
.lead-min {
  display: block; font-size: 1.05rem; font-weight: 750; color: var(--text);
  margin-bottom: 2px; font-variant-numeric: tabular-nums;
}

.grading-table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
.grading-table td, .grading-table th { padding: 7px 0; border-bottom: 1px solid var(--line-soft); vertical-align: middle; }
.grading-table th { text-align: left; font-weight: 500; }
.grading-table tr:last-child td, .grading-table tr:last-child th { border-bottom: none; }
.grading-table .w-num {
  white-space: nowrap; text-align: right; padding: 0 12px;
  font-weight: 700; font-variant-numeric: tabular-nums; width: 1%;
}
.grading-table .w-bar { width: 30%; min-width: 70px; }
.grading-table .w-bar span {
  display: block; height: 8px; border-radius: 4px;
  background: linear-gradient(90deg, var(--comp), var(--ai));
  min-width: 6px;
}

.q-list { margin: 0; padding-left: 20px; font-size: 0.92rem; }
.q-list li { padding: 3px 0; }

/* ---------------------------------------------------------------- project */

.tracks { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 16px; margin-bottom: 16px; }
.tracks-2 { grid-template-columns: 1fr 1fr; }
.track {
  background: var(--panel); border: 1px solid var(--line);
  border-top: 3px solid var(--muted);
  border-radius: var(--radius); padding: 18px 20px;
}
.track h2 { margin-bottom: 6px; }
.track p { margin: 0; font-size: 0.89rem; color: var(--muted); }
.track-id {
  margin: 0 0 8px; font-size: 0.72rem; font-weight: 700;
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--muted);
}
.t-comp { border-top-color: var(--comp); }
.t-comp .track-id { color: var(--comp-ink); }
.t-ai { border-top-color: var(--ai); }
.t-ai .track-id { color: var(--ai-ink); }

.col2-project { grid-template-columns: 1.2fr 1fr; }

.std-list { list-style: none; margin: 0; padding: 0; font-size: 0.89rem; }
.std-list li { padding: 5px 0 5px 24px; position: relative; border-bottom: 1px solid var(--line-soft); }
.std-list li:last-child { border-bottom: none; }
.std-list li::before {
  content: "✓"; position: absolute; left: 2px; top: 5px;
  font-weight: 700; color: var(--comp-ink); font-size: 0.85em;
}

.timeline { list-style: none; margin: 4px 0 14px; padding: 0; position: relative; }
.timeline::before {
  content: ""; position: absolute; left: 5px; top: 8px; bottom: 8px;
  width: 2px; background: linear-gradient(to bottom, var(--comp), var(--ai));
  border-radius: 1px;
}
.tl-item {
  position: relative; padding: 5px 0 5px 26px;
  display: flex; flex-wrap: wrap; gap: 8px; align-items: baseline;
  font-size: 0.9rem;
}
.tl-dot {
  position: absolute; left: 0; top: 11px;
  width: 12px; height: 12px; border-radius: 50%;
  background: var(--panel); border: 3px solid var(--comp);
}
.tl-item:nth-child(n+5) .tl-dot { border-color: var(--ai); }
.tl-item time { color: var(--muted); font-weight: 600; font-size: 0.84rem; flex: 0 0 52px; }
.tl-id {
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.04em;
  background: var(--panel-2); color: var(--muted);
  border-radius: 5px; padding: 1px 7px;
}
.tl-major .tl-id { background: var(--amber-soft); color: var(--amber-ink); }
.tl-major .tl-name { font-weight: 650; }

/* ---------------------------------------------------------------- policies */

.policy-stance {
  font-family: var(--serif); font-style: italic; font-size: 1.05rem;
  margin: 0 0 12px; color: color-mix(in srgb, var(--text) 88%, var(--muted));
}
.policy-list { margin: 0; padding-left: 20px; font-size: 0.92rem; }
.policy-list li { padding: 3px 0; }

.policy-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.policy-grid .panel { margin-bottom: 0; }
.policy-grid p { margin: 0; font-size: 0.89rem; color: var(--muted); }

/* ---------------------------------------------------------------- papers page */

.papers-index h1 { font-size: 2rem; font-weight: 800; letter-spacing: -0.02em; }
.papers-week {
  background: var(--panel); border: 1px solid var(--line);
  border-left-width: 3px; border-radius: var(--radius);
  padding: 18px 22px; margin-bottom: 14px;
}
.papers-week.m-comp { border-left-color: var(--comp); }
.papers-week.m-ai { border-left-color: var(--ai); }
.papers-week h2 { font-size: 1.1rem; margin-bottom: 2px; }
.wk-tag {
  display: inline-block; margin-right: 6px;
  font-size: 0.76rem; font-weight: 700; color: var(--muted);
  font-variant-numeric: tabular-nums; letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* ---------------------------------------------------------------- footer */

.site-foot {
  border-top: 1px solid var(--line-soft);
  margin-top: 40px; padding: 32px 0 44px;
  font-size: 0.86rem; color: var(--muted);
}
.foot-grid { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 24px; }
.foot-meta { text-align: right; }

/* ---------------------------------------------------------------- responsive */

@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; gap: 24px; }
  .instructor-card { max-width: 420px; }
  .tracks, .tracks-2, .lead-blocks { grid-template-columns: 1fr; }
  .col2, .col2-project, .policy-grid, .learn-grid { grid-template-columns: 1fr; }
  .sched-toc { grid-template-columns: 1fr; gap: 14px; }
  .prereq-list > div { grid-template-columns: 1fr; gap: 2px; }
  .foot-grid { grid-template-columns: 1fr; gap: 12px; }
  .foot-meta { text-align: left; }
  .now-grid { grid-template-columns: 1fr 1fr; }
  .now-class-panel { grid-column: 1 / -1; }
}

@media (max-width: 700px) {
  .hero { padding-top: 40px; }
  .duality-panel { grid-template-columns: 1fr; }
  .d-card-ai { text-align: left; }
  .brand-sub { display: none; }
  .site-head nav { flex-wrap: wrap; height: auto; min-height: 48px; padding: 8px 0; row-gap: 0; }
  .nav-links {
    width: 100%; flex-wrap: nowrap; overflow-x: auto;
    padding: 2px 0; scrollbar-width: none;
  }
  .nav-links::-webkit-scrollbar { display: none; }
  .nav-links a { flex: 0 0 auto; padding: 5px 7px; font-size: 0.85rem; }
  #theme-toggle { flex: 0 0 auto; }
  .module-divider, .week { scroll-margin-top: 106px; }
  .now-grid { grid-template-columns: 1fr; }
  .now-class-panel { grid-column: auto; }
  .now-heading { align-items: flex-start; flex-direction: column; gap: 2px; }

  .week { grid-template-columns: 1fr; gap: 8px; padding: 16px; }
  .week-rail { flex-direction: row; align-items: baseline; gap: 10px; }
  .wk-num { font-size: 1.1rem; }
  .week-rail::after { content: ""; flex: 1; border-bottom: 1px solid var(--line-soft); }
  .venue { margin-left: 6px; }
  .section-head { flex-direction: column; align-items: flex-start; }
}

/* ---------------------------------------------------------------- print */

@media print {
  :root { --bg: #fff; --panel: #fff; --panel-2: #f3f3f3; --line: #ccc; --line-soft: #ddd; }
  .site-head, .skip-link, #theme-toggle, .sched-tools, .site-foot .foot-meta { display: none !important; }
  body { font-size: 11px; }
  .hero { padding: 12px 0; }
  .week, .panel, .track, .papers-week { box-shadow: none; break-inside: avoid; }
  .week.past { opacity: 1; }
  a { color: inherit; text-decoration: none; }
  .section { padding: 14px 0; }
}