/* ==========================================================================
   Academic Portal — design system
   Mohsin Furkh Dar · School of Computer Science, UPES

   One stylesheet for every shell page: home, course indexes, research,
   blog, about. Individual lecture documents keep their own styles.

   Contents
     01  Tokens
     02  Reset & base
     03  Typography
     04  Layout primitives
     05  Masthead & navigation
     06  Search
     07  Index lists  (courses, units, posts)
     08  Resource lists
     09  Course masthead & breadcrumbs
     10  Prose, tables, callouts
     11  Footer
     12  Utilities
     13  Motion & print
   ========================================================================== */


/* --- 01  Tokens ---------------------------------------------------------- */

:root {
  /* Paper — warm, low-chroma neutrals. Never pure white. */
  --bg:            #faf8f5;
  --bg-sunken:     #f4f1ec;
  --surface:       #ffffff;
  --fg:            #191713;
  --fg-secondary:  #46423b;
  --fg-muted:      #777166;
  --fg-faint:      #8b8477;  /* separators and hairlines only */
  --border:        #e3ded4;
  --border-strong: #cdc6b8;

  /* A single accent: burnt sienna. Used for state, never for decoration. */
  --accent:        #97431f;
  --accent-hover:  #7d3617;
  --accent-wash:   #f6ece5;

  --focus:         #97431f;

  /* Type */
  --font-display: Newsreader, Georgia, "Times New Roman", serif;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
               "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
               "Liberation Mono", monospace;

  --text-xs:   0.75rem;    /* 12 — labels, eyebrows          */
  --text-sm:   0.8125rem;  /* 13 — metadata                  */
  --text-base: 0.9375rem;  /* 15 — UI                        */
  --text-md:   1.0625rem;  /* 17 — body prose                */
  --text-lg:   1.375rem;   /* 22 — row titles                */
  --text-xl:   1.875rem;   /* 30 — section heads             */
  --text-2xl:  2.5rem;     /* 40 — page titles               */
  --text-3xl:  3.75rem;    /* 60 — hero                      */

  --leading-tight: 1.15;
  --leading-snug:  1.35;
  --leading-body:  1.65;

  --tracking-label: 0.1em;
  --tracking-tight: -0.02em;

  /* Space — 4px base */
  --sp-1: 0.25rem;  --sp-2: 0.5rem;   --sp-3: 0.75rem;  --sp-4: 1rem;
  --sp-5: 1.5rem;   --sp-6: 2rem;     --sp-7: 3rem;     --sp-8: 4rem;
  --sp-9: 6rem;     --sp-10: 8rem;

  /* Measure */
  --w-page:    72rem;   /* 1152 — full layouts   */
  --w-text:    44rem;   /* 704  — reading column */
  --w-gutter:  1.5rem;

  --radius:    3px;
  --radius-lg: 6px;

  --ease: cubic-bezier(0.2, 0, 0.1, 1);
  --dur:  160ms;
  --dur-slow: 260ms;

  --shadow-pop: 0 1px 2px rgba(25, 23, 19, 0.06),
                0 12px 32px -8px rgba(25, 23, 19, 0.16);

  color-scheme: light;
}

/* Dark is a designed palette, not an inversion: the paper goes to a warm
   near-black, the sienna lifts to stay legible, borders stay very quiet.
   System preference is honoured unless the reader has chosen light. */

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
  --bg:            #131211;
  --bg-sunken:     #0e0d0c;
  --surface:       #1b1a18;
  --fg:            #ece8e1;
  --fg-secondary:  #c2bcb1;
  --fg-muted:      #918a7e;
  --fg-faint:      #837c70;
  --border:        #2c2a26;
  --border-strong: #423f39;

  --accent:        #dd8a63;
  --accent-hover:  #e9a183;
  --accent-wash:   #2a1e18;

  --focus:         #dd8a63;

  --shadow-pop: 0 1px 2px rgba(0, 0, 0, 0.4),
                0 12px 32px -8px rgba(0, 0, 0, 0.6);

  color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg:            #131211;
  --bg-sunken:     #0e0d0c;
  --surface:       #1b1a18;
  --fg:            #ece8e1;
  --fg-secondary:  #c2bcb1;
  --fg-muted:      #918a7e;
  --fg-faint:      #837c70;
  --border:        #2c2a26;
  --border-strong: #423f39;

  --accent:        #dd8a63;
  --accent-hover:  #e9a183;
  --accent-wash:   #2a1e18;

  --focus:         #dd8a63;

  --shadow-pop: 0 1px 2px rgba(0, 0, 0, 0.4),
                0 12px 32px -8px rgba(0, 0, 0, 0.6);

  color-scheme: dark;
}


/* --- 02  Reset & base ---------------------------------------------------- */

*, *::before, *::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  overflow-wrap: break-word;
}

h1, h2, h3, h4, h5, h6 { margin: 0; font-weight: 500; }
p, ul, ol, dl, figure, blockquote, table { margin: 0; }
ul, ol { padding: 0; list-style: none; }
img, svg, video { max-width: 100%; height: auto; display: block; }
svg { flex: none; }

a { color: inherit; text-decoration: none; }

button {
  font: inherit; color: inherit; background: none;
  border: 0; padding: 0; margin: 0; cursor: pointer;
}

input { font: inherit; color: inherit; }

hr {
  border: 0;
  border-top: 1px solid var(--border);
  margin: var(--sp-7) 0;
}

::selection { background: var(--accent-wash); color: var(--fg); }
:root[data-theme="dark"] ::selection { background: #3a2a21; }

:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 3px;
  border-radius: 2px;
}
:focus:not(:focus-visible) { outline: none; }

.skip-link {
  position: absolute; left: var(--sp-4); top: var(--sp-4);
  transform: translateY(-160%);
  background: var(--fg); color: var(--bg);
  padding: var(--sp-2) var(--sp-4);
  border-radius: var(--radius);
  font-size: var(--text-sm); font-weight: 500;
  z-index: 200;
  transition: transform var(--dur) var(--ease);
}
.skip-link:focus { transform: translateY(0); }


/* --- 03  Typography ------------------------------------------------------ */

/* Eyebrow: small, spaced, uppercase. The connective tissue of the whole site. */
.label {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 500;
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
  color: var(--fg-muted);
}

.label--accent { color: var(--accent); }

.display {
  font-family: var(--font-display);
  font-weight: 400;
  line-height: var(--leading-tight);
  letter-spacing: var(--tracking-tight);
}

.mono { font-family: var(--font-mono); font-size: 0.92em; }

.lede {
  font-size: var(--text-md);
  line-height: var(--leading-body);
  color: var(--fg-secondary);
  max-width: var(--w-text);
}

/* Status markers — typographic, never pill-shaped chips. */
.status {
  display: inline-flex; align-items: center; gap: 0.4em;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
  color: var(--fg-muted);
  white-space: nowrap;
}
.status::before {
  content: ""; width: 5px; height: 5px; border-radius: 50%;
  background: var(--fg-faint);
}
.status--current { color: var(--accent); }
.status--current::before { background: var(--accent); }
.status--empty::before { background: none; box-shadow: inset 0 0 0 1px var(--fg-faint); }

/* Inline link inside prose */
.link {
  color: inherit;
  text-decoration: underline;
  text-decoration-color: var(--border-strong);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.22em;
  transition: text-decoration-color var(--dur) var(--ease), color var(--dur) var(--ease);
}
.link:hover { color: var(--accent); text-decoration-color: var(--accent); }

/* External link marker */
.link-out::after {
  content: "↗";
  display: inline-block;
  margin-left: 0.28em;
  font-size: 0.85em;
  color: var(--fg-faint);
}


/* --- 04  Layout primitives ----------------------------------------------- */

.wrap {
  width: 100%;
  max-width: var(--w-page);
  margin-inline: auto;
  padding-inline: var(--w-gutter);
}

.wrap--text { max-width: calc(var(--w-text) + var(--w-gutter) * 2); }

.section { padding-block: var(--sp-8); }
.section + .section { padding-top: 0; }

/* Section head: rule above, label + title. Repeated everywhere. */
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--sp-5);
  flex-wrap: wrap;
  padding-top: var(--sp-4);
  border-top: 1px solid var(--fg);
  margin-bottom: var(--sp-6);
}

.section-head__title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
}

.section-head__note {
  font-size: var(--text-sm);
  color: var(--fg-muted);
}

/* Two-column editorial split: sticky aside + content */
.split {
  display: grid;
  grid-template-columns: 14rem minmax(0, 1fr);
  gap: var(--sp-8);
  align-items: start;
}
.split__aside { position: sticky; top: 5.5rem; }

@media (max-width: 62rem) {
  .split { grid-template-columns: 1fr; gap: var(--sp-5); }
  .split__aside { position: static; }
}


/* --- 05  Masthead & navigation ------------------------------------------- */

.masthead {
  position: sticky; top: 0; z-index: 100;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(12px);
  border-bottom: 1px solid var(--border);
}
@supports not (backdrop-filter: blur(1px)) {
  .masthead { background: var(--bg); }
}

.masthead__inner {
  display: flex; align-items: center; gap: var(--sp-5);
  height: 4rem;
}

.brand {
  display: flex; flex-direction: column; gap: 1px;
  margin-right: auto;
  line-height: 1.25;
}
.brand__name {
  font-family: var(--font-display);
  font-size: 1.0625rem;
  letter-spacing: -0.01em;
}
.brand__role {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--fg-muted);
}
.brand:hover .brand__name { color: var(--accent); }

@media (max-width: 30rem) {
  /* keep the masthead one line tall on a phone */
  .brand__role { display: none; }
  .masthead__inner { height: 3.5rem; gap: var(--sp-3); }
  .nav[data-open] { inset-block-start: 3.5rem; }
}

.nav { display: flex; align-items: center; gap: var(--sp-5); }

.nav__link {
  position: relative;
  font-size: var(--text-base);
  color: var(--fg-secondary);
  padding-block: var(--sp-1);
  transition: color var(--dur) var(--ease);
}
.nav__link::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -2px;
  height: 1px; background: currentColor;
  transform: scaleX(0); transform-origin: left;
  transition: transform var(--dur-slow) var(--ease);
}
.nav__link:hover { color: var(--fg); }
.nav__link:hover::after { transform: scaleX(1); }
.nav__link[aria-current="page"] { color: var(--fg); }
.nav__link[aria-current="page"]::after {
  transform: scaleX(1); background: var(--accent);
}

.masthead__tools { display: flex; align-items: center; gap: var(--sp-2); }

.icon-btn {
  display: grid; place-items: center;
  width: 2.125rem; height: 2.125rem;
  border-radius: var(--radius);
  color: var(--fg-secondary);
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease);
}
.icon-btn:hover { background: var(--bg-sunken); color: var(--fg); }
.icon-btn svg { width: 17px; height: 17px; }

/* Theme toggle swaps which glyph is shown */
.theme-toggle .icon-moon { display: none; }
:root[data-theme="dark"] .theme-toggle .icon-moon { display: block; }
:root[data-theme="dark"] .theme-toggle .icon-sun { display: none; }

.nav-toggle { display: none; }

/* Search drawer: collapsed under the masthead until asked for. */
.masthead__search {
  display: grid;
  grid-template-rows: 0fr;
  border-top: 1px solid transparent;
  transition: grid-template-rows var(--dur-slow) var(--ease),
              border-color var(--dur-slow) var(--ease);
}
.masthead__search > * { overflow: hidden; min-height: 0; }
.masthead__search[data-open="true"] {
  grid-template-rows: 1fr;
  border-top-color: var(--border);
}
/* once open, the results panel must be allowed to overhang the drawer */
.masthead__search[data-open="true"] > * { overflow: visible; }
.masthead__search .search {
  max-width: none;
  padding-block: var(--sp-3);
}
@supports not (grid-template-rows: 0fr) {
  .masthead__search { display: none; }
  .masthead__search[data-open="true"] { display: block; }
}

@media (max-width: 54rem) {
  .nav-toggle { display: grid; }

  .nav {
    position: fixed; inset: 4rem 0 auto 0;
    flex-direction: column; align-items: stretch; gap: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: var(--sp-2) var(--w-gutter) var(--sp-5);
    box-shadow: var(--shadow-pop);
    transform: translateY(-8px);
    opacity: 0; visibility: hidden;
    transition: opacity var(--dur) var(--ease),
                transform var(--dur) var(--ease),
                visibility var(--dur);
  }
  .nav[data-open="true"] { opacity: 1; visibility: visible; transform: translateY(0); }

  .nav__link {
    padding: var(--sp-4) 0;
    font-size: var(--text-lg);
    font-family: var(--font-display);
    border-bottom: 1px solid var(--border);
  }
  .nav__link::after { display: none; }
  .nav__link[aria-current="page"] { color: var(--accent); }
}


/* --- 06  Search ---------------------------------------------------------- */

.search {
  position: relative;
  max-width: 38rem;
}

.search__field {
  display: flex; align-items: center; gap: var(--sp-3);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  padding: 0 var(--sp-4);
  transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}
.search__field:focus-within {
  border-color: var(--fg);
  box-shadow: 0 0 0 3px var(--accent-wash);
}

.search__icon { width: 16px; height: 16px; color: var(--fg-muted); }

.search__input {
  flex: 1; min-width: 0;
  border: 0; background: none; outline: none;
  padding: 0.875rem 0;
  font-size: var(--text-md);
}
.search__input::placeholder { color: var(--fg-muted); }

/* the browser's own clear affordance duplicates .search__clear */
.search__input::-webkit-search-cancel-button,
.search__input::-webkit-search-decoration { -webkit-appearance: none; appearance: none; }

.search__hint {
  font-family: var(--font-mono); font-size: var(--text-xs);
  color: var(--fg-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.125rem 0.375rem;
}
@media (max-width: 40rem) { .search__hint { display: none; } }

.search__clear { display: none; color: var(--fg-muted); }
.search__clear svg { width: 15px; height: 15px; }
.search[data-has-query="true"] .search__clear { display: block; }
.search[data-has-query="true"] .search__hint { display: none; }

/* Results panel */
.search__panel {
  position: absolute; top: calc(100% + 6px); left: 0; right: 0;
  z-index: 90;
  background: var(--surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-pop);
  max-height: min(28rem, 60vh);
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: var(--sp-2);
  display: none;
}
.search[data-open="true"] .search__panel { display: block; }

.search__status {
  padding: var(--sp-4);
  font-size: var(--text-sm);
  color: var(--fg-muted);
}

.search__group + .search__group { margin-top: var(--sp-2); }

.search__group-head {
  padding: var(--sp-3) var(--sp-3) var(--sp-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
  color: var(--fg-muted);
  border-top: 1px solid var(--border);
}
.search__group:first-child .search__group-head { border-top: 0; }

.search__hit {
  display: block;
  padding: var(--sp-3);
  border-radius: var(--radius);
  transition: background var(--dur) var(--ease);
}
.search__hit:hover,
.search__hit[data-active="true"] { background: var(--bg-sunken); }
.search__hit[data-active="true"] { outline: none; }

.search__hit-title {
  font-size: var(--text-base);
  line-height: 1.35;
  color: var(--fg);
}
.search__hit-title mark {
  background: var(--accent-wash);
  color: var(--accent);
  padding: 0 1px;
  border-radius: 2px;
}
:root[data-theme="dark"] .search__hit-title mark { color: var(--accent); }

.search__hit-path {
  display: flex; align-items: center; flex-wrap: wrap;
  gap: 0.3em;
  margin-top: 3px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
}
.search__hit-path span:not(:last-child)::after {
  content: " ›"; color: var(--fg-faint);
}

.search__foot {
  display: flex; justify-content: space-between; align-items: center;
  gap: var(--sp-4);
  padding: var(--sp-3);
  margin-top: var(--sp-2);
  border-top: 1px solid var(--border);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
}


/* --- 07  Index lists ----------------------------------------------------- */

/* The core pattern of the site: a numbered, ruled list of things.
   Used for courses, units, posts, research items. Not a card grid. */

.index { border-top: 1px solid var(--border); }

.row {
  display: grid;
  grid-template-columns: 3.25rem minmax(0, 1fr) auto;
  align-items: baseline;
  gap: var(--sp-4);
  padding: var(--sp-5) 0;
  border-bottom: 1px solid var(--border);
  position: relative;
  transition: background var(--dur) var(--ease);
}

a.row { cursor: pointer; }

a.row::before {
  content: "";
  position: absolute;
  inset: 0 calc(var(--sp-4) * -1);
  background: var(--bg-sunken);
  opacity: 0;
  border-radius: var(--radius);
  transition: opacity var(--dur) var(--ease);
  pointer-events: none;
}
a.row:hover::before { opacity: 1; }
a.row > * { position: relative; }

.row__no {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  font-variant-numeric: tabular-nums;
  transition: color var(--dur) var(--ease);
}
a.row:hover .row__no { color: var(--accent); }

.row__body { min-width: 0; }

.row__title {
  display: block;
  font-family: var(--font-display);
  font-size: var(--text-lg);
  line-height: var(--leading-snug);
  letter-spacing: var(--tracking-tight);
  transition: transform var(--dur-slow) var(--ease);
}
a.row:hover .row__title { transform: translateX(3px); }

.row__desc {
  display: block;
  margin-top: var(--sp-2);
  font-size: var(--text-base);
  color: var(--fg-muted);
  line-height: 1.55;
  max-width: 46rem;
}

.row__meta {
  display: flex; align-items: center; flex-wrap: wrap;
  gap: 0.45em;
  margin-top: var(--sp-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
  letter-spacing: 0.02em;
}
.row__meta > span:not(:last-child)::after {
  content: " ·"; color: var(--fg-faint); margin-left: 0.3em;
}

.row__aside {
  display: flex; align-items: center; gap: var(--sp-4);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  white-space: nowrap;
}

.row__arrow {
  width: 16px; height: 16px;
  color: var(--fg-faint);
  opacity: 0;
  transform: translateX(-4px);
  transition: opacity var(--dur-slow) var(--ease),
              transform var(--dur-slow) var(--ease),
              color var(--dur) var(--ease);
  align-self: center;
}
a.row:hover .row__arrow,
a.row:focus-visible .row__arrow {
  opacity: 1; transform: translateX(0); color: var(--accent);
}

/* Muted variant for archived / unavailable entries */
.row--quiet .row__title { color: var(--fg-secondary); font-size: var(--text-md); }
.row--quiet { padding-block: var(--sp-4); }

.row[aria-disabled="true"] { cursor: default; }
.row[aria-disabled="true"] .row__title { color: var(--fg-muted); }
.row[aria-disabled="true"]::before { display: none; }

@media (max-width: 40rem) {
  .row {
    grid-template-columns: 2.25rem minmax(0, 1fr);
    gap: var(--sp-3);
    padding: var(--sp-4) 0;
  }
  .row__title { font-size: var(--text-md); }
  .row__aside {
    grid-column: 2;
    margin-top: var(--sp-2);
    font-size: var(--text-xs);
  }
  .row__arrow { display: none; }
  a.row:hover .row__title { transform: none; }
}

/* Session grouping on the homepage */
.session + .session { margin-top: var(--sp-8); }

.session__head {
  display: flex; align-items: baseline; justify-content: space-between;
  gap: var(--sp-4); flex-wrap: wrap;
  padding-bottom: var(--sp-3);
  border-bottom: 1px solid var(--fg);
}
.session--quiet .session__head { border-bottom-color: var(--border-strong); }

.session__name {
  display: flex; align-items: baseline; gap: var(--sp-3);
  flex-wrap: wrap;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
}
.session--quiet .session__name { font-weight: 500; color: var(--fg-muted); }

.session__years {
  font-weight: 400;
  color: var(--fg-muted);
  letter-spacing: 0.05em;
}

.session__count {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
}


/* --- 08  Resource lists -------------------------------------------------- */

/* Resource types: a definition list, not a grid of icon cards. */
.resources { border-top: 1px solid var(--border); }

.resource {
  display: grid;
  grid-template-columns: minmax(0, 15rem) minmax(0, 1fr);
  gap: var(--sp-4) var(--sp-6);
  padding: var(--sp-5) 0;
  border-bottom: 1px solid var(--border);
}

.resource__term {
  display: flex; align-items: baseline; gap: var(--sp-3);
}
.resource__name {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
}
.resource__desc {
  margin-top: var(--sp-1);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  line-height: 1.5;
}

.resource__items { display: flex; flex-direction: column; gap: 2px; }

@media (max-width: 48rem) {
  .resource { grid-template-columns: 1fr; gap: var(--sp-3); padding: var(--sp-4) 0; }
}

/* A single resource link — the smallest interactive unit on the site */
.file {
  display: flex; align-items: center; gap: var(--sp-3);
  padding: var(--sp-2) var(--sp-3);
  margin-inline: calc(var(--sp-3) * -1);
  border-radius: var(--radius);
  font-size: var(--text-base);
  color: var(--fg-secondary);
  line-height: 1.45;
  min-height: 2.5rem;
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease);
}
.file:hover { background: var(--bg-sunken); color: var(--fg); }

.file__kind {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--fg-muted);
  border: 1px solid var(--border);
  border-radius: 2px;
  padding: 0.125rem 0.3rem;
  flex: none;
  min-width: 2.75rem;
  text-align: center;
}
.file:hover .file__kind { border-color: var(--border-strong); color: var(--fg-secondary); }

.file__name { flex: 1; min-width: 0; }

.file__arrow {
  width: 14px; height: 14px; flex: none;
  color: var(--fg-faint);
  opacity: 0; transform: translateX(-3px);
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease);
}
.file:hover .file__arrow,
.file:focus-visible .file__arrow { opacity: 1; transform: translateX(0); }

.file[aria-disabled="true"] {
  color: var(--fg-faint);
  cursor: default;
  pointer-events: none;
}
.file[aria-disabled="true"] .file__kind { opacity: 0.5; }

/* Unit block on a course page: number, title, topics, then its files */
.unit {
  display: grid;
  grid-template-columns: 3.25rem minmax(0, 1fr);
  gap: var(--sp-4);
  padding: var(--sp-6) 0;
  border-bottom: 1px solid var(--border);
}
.unit:first-child { border-top: 1px solid var(--fg); }

.unit__no {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  font-variant-numeric: tabular-nums;
  padding-top: 0.35rem;
}

.unit__title {
  display: block;
  font-family: var(--font-display);
  font-size: var(--text-lg);
  line-height: var(--leading-snug);
  letter-spacing: var(--tracking-tight);
}

.unit__topics {
  display: block;
  margin-top: var(--sp-2);
  font-size: var(--text-base);
  color: var(--fg-muted);
  line-height: 1.55;
  max-width: 46rem;
}

.unit__meta {
  margin-top: var(--sp-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
}

.unit__files { margin-top: var(--sp-4); }

@media (max-width: 40rem) {
  .unit { grid-template-columns: 2.25rem minmax(0, 1fr); gap: var(--sp-3); padding: var(--sp-5) 0; }
  .unit__title { font-size: var(--text-md); }
}


/* Entries: one lecture, lab, book or link inside a unit. The workhorse of
   every course page. Title carries the primary link; alternative formats sit
   to the right as small typographic actions. */

.entries { border-top: 1px solid var(--border); }

.entry {
  display: grid;
  grid-template-columns: 2.5rem minmax(0, 1fr) auto;
  align-items: baseline;
  gap: var(--sp-3) var(--sp-4);
  padding: var(--sp-3) 0;
  border-bottom: 1px solid var(--border);
}

.entry__no {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
  font-variant-numeric: tabular-nums;
}

.entry__title {
  display: block;
  font-size: var(--text-base);
  line-height: 1.5;
  color: var(--fg);
}
a.entry__title { transition: color var(--dur) var(--ease); }
a.entry__title:hover { color: var(--accent); }
a.entry__title::after {
  content: "";
  display: inline-block;
  width: 0.5em; height: 0.5em;
  margin-left: 0.5em;
  border-top: 1px solid currentColor;
  border-right: 1px solid currentColor;
  transform: rotate(45deg) translate(-2px, 1px);
  opacity: 0;
  transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease);
}
a.entry__title:hover::after,
a.entry__title:focus-visible::after { opacity: 0.55; transform: rotate(45deg) translate(0, 0); }

.entry__note {
  display: block;
  margin-top: 3px;
  font-size: var(--text-sm);
  color: var(--fg-muted);
  line-height: 1.5;
  max-width: 54ch;
}

.entry__meta {
  display: block;
  margin-top: 2px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
}

.entry__acts {
  display: flex; align-items: center; gap: var(--sp-3);
  white-space: nowrap;
}

.act {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--fg-muted);
  border-bottom: 1px solid transparent;
  padding-bottom: 1px;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.act:hover { color: var(--accent); border-color: var(--accent); }
.act[aria-disabled="true"] {
  color: var(--fg-faint); pointer-events: none;
  text-decoration: line-through; text-decoration-thickness: 1px;
}

.entry--soon .entry__title { color: var(--fg-muted); }

@media (max-width: 40rem) {
  .entry { grid-template-columns: 2rem minmax(0, 1fr); gap: var(--sp-2) var(--sp-3); }
  .entry__acts { grid-column: 2; margin-top: var(--sp-1); }
  .entry__title { font-size: var(--text-base); }
  a.entry__title::after { display: none; }
}


/* --- 09  Course masthead & breadcrumbs ----------------------------------- */

.crumbs {
  display: flex; align-items: center; flex-wrap: wrap;
  gap: 0.4em;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--fg-muted);
  padding-top: var(--sp-6);
}
.crumbs a { transition: color var(--dur) var(--ease); }
.crumbs a:hover { color: var(--accent); }
.crumbs li:not(:last-child)::after {
  content: " /"; color: var(--fg-faint); margin-left: 0.4em;
}
.crumbs li:last-child { color: var(--fg); }

.page-head { padding-block: var(--sp-5) var(--sp-7); }

.page-head__title {
  font-family: var(--font-display);
  font-size: clamp(2rem, 6vw, var(--text-2xl));
  font-weight: 400;
  line-height: var(--leading-tight);
  letter-spacing: var(--tracking-tight);
  margin-top: var(--sp-3);
  max-width: 24ch;
}

.page-head__meta {
  display: flex; align-items: center; flex-wrap: wrap;
  gap: 0.5em;
  margin-top: var(--sp-4);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--fg-muted);
}
.page-head__meta > span:not(:last-child)::after {
  content: " ·"; color: var(--fg-faint); margin-left: 0.4em;
}

.page-head__lede { margin-top: var(--sp-5); }

.page-head__actions {
  display: flex; flex-wrap: wrap; gap: var(--sp-3);
  margin-top: var(--sp-6);
}

.btn {
  display: inline-flex; align-items: center; gap: var(--sp-2);
  padding: 0.625rem var(--sp-4);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: var(--surface);
  font-size: var(--text-base);
  color: var(--fg);
  min-height: 2.5rem;
  transition: border-color var(--dur) var(--ease),
              background var(--dur) var(--ease),
              color var(--dur) var(--ease);
}
.btn:hover { border-color: var(--fg); background: var(--bg-sunken); }
.btn svg { width: 15px; height: 15px; color: var(--fg-muted); }
.btn:hover svg { color: var(--accent); }

.btn--primary {
  background: var(--fg); color: var(--bg); border-color: var(--fg);
}
.btn--primary:hover { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn--primary svg { color: currentColor; }
.btn--primary:hover svg { color: currentColor; }

/* Course-page section navigation (sticky aside) */
.toc { display: flex; flex-direction: column; gap: 1px; }
.toc__link {
  padding: var(--sp-2) 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--fg-muted);
  border-left: 1px solid var(--border);
  padding-left: var(--sp-3);
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.toc__link:hover { color: var(--fg); border-color: var(--border-strong); }
.toc__link[aria-current="true"] { color: var(--accent); border-color: var(--accent); }

@media (max-width: 62rem) {
  .toc {
    flex-direction: row; flex-wrap: wrap; gap: var(--sp-2);
    padding-bottom: var(--sp-4);
    border-bottom: 1px solid var(--border);
  }
  .toc__link {
    border-left: 0; padding: var(--sp-2) var(--sp-3);
    border: 1px solid var(--border); border-radius: var(--radius);
  }
  .toc__link[aria-current="true"] { border-color: var(--accent); }
}


/* --- 10  Prose, tables, callouts ----------------------------------------- */

.prose {
  max-width: var(--w-text);
  font-size: var(--text-md);
  line-height: var(--leading-body);
  color: var(--fg-secondary);
}
.prose > * + * { margin-top: var(--sp-4); }
.prose h2 {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  color: var(--fg);
  margin-top: var(--sp-7);
  letter-spacing: var(--tracking-tight);
}
.prose h3 {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  color: var(--fg);
  margin-top: var(--sp-6);
}
.prose ul { list-style: none; }
.prose li { position: relative; padding-left: var(--sp-5); }
.prose li + li { margin-top: var(--sp-2); }
.prose ul > li::before {
  content: "—";
  position: absolute; left: 0;
  color: var(--fg-faint);
}
.prose ol { counter-reset: n; }
.prose ol > li { counter-increment: n; }
.prose ol > li::before {
  content: counter(n, decimal-leading-zero);
  position: absolute; left: 0;
  font-family: var(--font-mono); font-size: var(--text-xs);
  color: var(--fg-faint);
  top: 0.28em;
}
.prose strong { color: var(--fg); font-weight: 600; }
.prose code {
  font-family: var(--font-mono); font-size: 0.875em;
  background: var(--bg-sunken);
  border: 1px solid var(--border);
  border-radius: 2px;
  padding: 0.1em 0.35em;
  color: var(--fg);
}

/* Plain list of facts: term on the left, value on the right */
.facts { border-top: 1px solid var(--border); }
.facts__row {
  display: grid;
  grid-template-columns: minmax(0, 12rem) minmax(0, 1fr);
  gap: var(--sp-3) var(--sp-5);
  padding: var(--sp-4) 0;
  border-bottom: 1px solid var(--border);
  font-size: var(--text-base);
}
.facts__term {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
  color: var(--fg-muted);
  padding-top: 0.2em;
}
.facts__val { color: var(--fg-secondary); line-height: 1.55; }
@media (max-width: 40rem) {
  .facts__row { grid-template-columns: 1fr; gap: var(--sp-2); }
}

.note {
  border-left: 2px solid var(--border-strong);
  padding: var(--sp-1) 0 var(--sp-1) var(--sp-5);
  font-size: var(--text-base);
  color: var(--fg-muted);
  line-height: 1.6;
  max-width: var(--w-text);
}
.note--accent { border-left-color: var(--accent); }

.empty {
  padding: var(--sp-7) 0;
  font-size: var(--text-base);
  color: var(--fg-muted);
  border-bottom: 1px solid var(--border);
}
.empty__title { color: var(--fg-secondary); }
.empty__hint { margin-top: var(--sp-2); font-size: var(--text-sm); }


/* --- 10b  Homepage hero -------------------------------------------------- */

.hero { padding-block: var(--sp-9) var(--sp-8); }

.hero__eyebrow {
  display: flex; align-items: center; flex-wrap: wrap; gap: 0.5em;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
  color: var(--fg-muted);
}
.hero__eyebrow > span:not(:last-child)::after {
  content: " \00b7"; color: var(--fg-faint); margin-left: 0.4em;
}

.hero__title {
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(2.25rem, 7vw, var(--text-3xl));
  line-height: 1.05;
  letter-spacing: -0.028em;
  margin-top: var(--sp-5);
  max-width: 18ch;
  text-wrap: balance;
}

.hero__lede {
  margin-top: var(--sp-5);
  font-size: var(--text-md);
  line-height: var(--leading-body);
  color: var(--fg-secondary);
  max-width: 52ch;
}

.hero__search { margin-top: var(--sp-7); }

.hero__jump {
  display: flex; align-items: center; flex-wrap: wrap;
  gap: var(--sp-2) var(--sp-4);
  margin-top: var(--sp-5);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--fg-muted);
}
.hero__jump a {
  border-bottom: 1px solid var(--border-strong);
  padding-bottom: 2px;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.hero__jump a:hover { color: var(--accent); border-color: var(--accent); }

@media (max-width: 40rem) {
  .hero { padding-block: var(--sp-6) var(--sp-5); }
  .hero__title { max-width: none; }
  /* the name is already in the masthead two lines above */
  .hero__eyebrow-name { display: none; }
  .hero__eyebrow { font-size: 0.6875rem; line-height: 1.7; }
  .hero__lede { font-size: var(--text-base); }
  .hero__search { margin-top: var(--sp-6); }
}

/* Two editorial columns that collapse to one — research + writing */
.duo {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--sp-8);
}
@media (max-width: 54rem) {
  .duo { grid-template-columns: 1fr; gap: var(--sp-7); }
}


/* --- 11  Footer ---------------------------------------------------------- */

.site-footer {
  margin-top: var(--sp-9);
  border-top: 1px solid var(--fg);
  padding-block: var(--sp-7) var(--sp-6);
}

.site-footer__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) repeat(2, minmax(0, 1fr));
  gap: var(--sp-6) var(--sp-5);
}

.site-footer__name {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  letter-spacing: var(--tracking-tight);
}
.site-footer__role {
  margin-top: var(--sp-2);
  font-size: var(--text-sm);
  color: var(--fg-muted);
  line-height: 1.5;
}

.site-footer__col-head {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-label);
  text-transform: uppercase;
  color: var(--fg-muted);
  margin-bottom: var(--sp-3);
}

.site-footer__links { display: flex; flex-direction: column; gap: var(--sp-2); }
.site-footer__links a {
  font-size: var(--text-base);
  color: var(--fg-secondary);
  width: fit-content;
  transition: color var(--dur) var(--ease);
}
.site-footer__links a:hover { color: var(--accent); }

.site-footer__base {
  display: flex; justify-content: space-between; flex-wrap: wrap;
  gap: var(--sp-4);
  margin-top: var(--sp-7);
  padding-top: var(--sp-4);
  border-top: 1px solid var(--border);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--fg-muted);
}

@media (max-width: 48rem) {
  .site-footer__grid { grid-template-columns: 1fr; gap: var(--sp-6); }
}


/* --- 12  Utilities ------------------------------------------------------- */

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap; border: 0;
}

.stack-2 > * + * { margin-top: var(--sp-2); }
.stack-4 > * + * { margin-top: var(--sp-4); }
.stack-6 > * + * { margin-top: var(--sp-6); }

.text-muted { color: var(--fg-muted); }
.no-js-hide { display: none; }


/* --- 13  Motion & print -------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

@media print {
  .masthead, .search, .site-footer, .toc, .row__arrow, .file__arrow { display: none !important; }
  body { background: #fff; color: #000; }
  a { text-decoration: underline; }
  .row, .unit, .resource { break-inside: avoid; }
}