/* =========================================================================
   SBTE 2.0 — Design system
   Concept: a technical drawing sheet. Deep ink background, blueprint-blue
   linework, amber "marker" for action/active state, IBM Plex Mono for
   every technical label (semester numbers, file sizes, the title block),
   Space Grotesk for display type. Branch accents are drawn from each
   discipline's own material: concrete ochre, iron rust, brass/copper,
   PCB solder-mask green, and circuit blueprint-blue for CS.
   ========================================================================= */

:root {
  color-scheme: dark;

  /* --- surfaces --- */
  --ink-950: #0a0e13;
  --ink-900: #10151d;
  --ink-850: #141b24;
  --ink-800: #1b232e;
  --ink-700: #262f3b;
  --hairline: rgba(63, 169, 245, 0.16);
  --hairline-strong: rgba(63, 169, 245, 0.34);

  /* --- accents --- */
  --blueprint: #3fa9f5;
  --blueprint-dim: rgba(63, 169, 245, 0.13);
  --marker: #ffb020;
  --marker-dim: rgba(255, 176, 32, 0.15);
  --redline: #ff5d5d;
  --redline-dim: rgba(255, 93, 93, 0.13);

  /* --- text --- */
  --paper: #edeff2;
  --paper-dim: #b7c0cc;
  --graphite: #8b95a1;
  --graphite-dim: #5b6672;

  /* --- branch materials --- */
  --civil: #d4a657;
  --cse: #3fa9f5;
  --mechanical: #e8734a;
  --electrical: #f5c542;
  --electronics: #5bc49f;

  /* --- type --- */
  --font-display: "Space Grotesk", "Segoe UI", sans-serif;
  --font-body: "IBM Plex Sans", "Segoe UI", sans-serif;
  --font-mono: "IBM Plex Mono", "Courier New", monospace;

  /* --- spacing scale --- */
  --sp-1: 4px;
  --sp-2: 8px;
  --sp-3: 12px;
  --sp-4: 16px;
  --sp-5: 24px;
  --sp-6: 32px;
  --sp-7: 48px;
  --sp-8: 64px;
  --sp-9: 96px;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 18px;

  --container: 1180px;
  --header-h: 68px;
}

/* -------------------------------------------------------------------- */
/* Reset                                                                 */
/* -------------------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  background: var(--ink-950);
  color: var(--paper);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
ul { list-style: none; margin: 0; padding: 0; }
input { font: inherit; color: inherit; }

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  margin: 0;
  letter-spacing: -0.01em;
}

::selection { background: var(--marker); color: var(--ink-950); }

:focus-visible {
  outline: 2px solid var(--marker);
  outline-offset: 2px;
  border-radius: 4px;
}

/* Keyboard-only "skip to content" link — invisible until focused, so a
   keyboard/screen-reader user can jump past the header and breadcrumb
   without a mouse user ever seeing it. */
.skip-link {
  position: absolute;
  top: -48px;
  left: var(--sp-4);
  z-index: 100;
  background: var(--marker);
  color: var(--ink-950);
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 600;
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  transition: top 0.15s ease;
}
.skip-link:focus {
  top: var(--sp-3);
}

/* Fixed 3D canvas sits behind everything */
#bg-canvas {
  position: fixed;
  inset: 0;
  z-index: -1;
  display: block;
}

.bg-grid {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background-image:
    linear-gradient(var(--hairline) 1px, transparent 1px),
    linear-gradient(90deg, var(--hairline) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 0%, #000 40%, transparent 90%);
  opacity: 0.5;
}

/* -------------------------------------------------------------------- */
/* Layout                                                                */
/* -------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--sp-5);
}

main { display: block; min-height: calc(100vh - var(--header-h)); padding-bottom: var(--sp-9); }

.eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--blueprint);
}

.section-head { margin: var(--sp-8) 0 var(--sp-5); }
.section-head h2 { font-size: 26px; }
.section-head p { color: var(--graphite); margin-top: var(--sp-2); }

.grid {
  display: grid;
  gap: var(--sp-4);
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
}

.grid--tight { grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); }
.grid--wide { grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); }

/* -------------------------------------------------------------------- */
/* Header — the sheet's top border strip                                */
/* -------------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  display: flex;
  align-items: center;
  background: rgba(10, 14, 19, 0.86);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--hairline);
}

.site-header .container { display: flex; align-items: center; gap: var(--sp-5); height: 100%; }

.brand { display: flex; align-items: center; gap: var(--sp-3); flex-shrink: 0; }
.brand img {
  width: 36px; height: 36px; border-radius: var(--radius-sm);
  border: 1px solid var(--hairline-strong);
}
.brand-name { font-family: var(--font-display); font-weight: 700; font-size: 17px; line-height: 1.1; }
.brand-sub {
  display: block; font-family: var(--font-mono); font-size: 10px; letter-spacing: 0.06em;
  color: var(--graphite); text-transform: uppercase; margin-top: 2px;
}

.main-nav { display: flex; align-items: center; gap: var(--sp-5); margin-left: var(--sp-4); flex: 1; }
.main-nav a {
  font-size: 14px; color: var(--paper-dim); padding: var(--sp-2) 0; position: relative;
}
.main-nav a:hover { color: var(--paper); }

/* Mobile nav overlay. position:fixed here is unconditional (not inside a
   media query) so it is ALWAYS taken out of .site-header's flex flow --
   without this it renders as a bare, visible flex sibling of .container
   at any width wider than the 860px breakpoint below, since header itself
   is display:flex. Hidden by default via opacity/pointer-events (not
   display:none) so the open/close transition can actually animate; the
   toggle button that's the only way to add .is-open is itself hidden
   above 860px, so this never becomes reachable at desktop widths. */
.mobile-nav {
  position: fixed; inset: var(--header-h) 0 0 0; z-index: 49;
  background: var(--ink-950);
  border-top: 1px solid var(--hairline);
  padding: var(--sp-5);
  transform: translateY(-8px);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.18s ease, transform 0.18s ease;
}
.mobile-nav.is-open { opacity: 1; transform: translateY(0); pointer-events: auto; }
.mobile-nav a {
  display: block; padding: var(--sp-4) 0; font-size: 18px; font-family: var(--font-display);
  border-bottom: 1px solid var(--hairline);
}

.header-search {
  margin-left: auto;
  display: flex; align-items: center; gap: var(--sp-2);
  border: 1px solid var(--hairline-strong);
  background: var(--ink-900);
  border-radius: var(--radius-md);
  padding: var(--sp-2) var(--sp-3);
  min-width: 220px;
  transition: border-color 0.15s ease;
}
.header-search:focus-within { border-color: var(--blueprint); }
.header-search input {
  background: none; border: 0; outline: none; color: var(--paper);
  font-size: 13px; width: 100%;
}
.header-search input::placeholder { color: var(--graphite-dim); }
.header-search button {
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0; color: var(--graphite); width: 16px; height: 16px;
  padding: 0; cursor: pointer;
}
.header-search button:hover, .header-search button:focus-visible { color: var(--blueprint); }
.header-search svg { flex-shrink: 0; width: 16px; height: 16px; }

.menu-toggle { display: none; }

/* -------------------------------------------------------------------- */
/* Title block — the recurring signature element                        */
/* Modeled on the stamp in the corner of a real engineering drawing.    */
/* -------------------------------------------------------------------- */
.title-block {
  border: 1px solid var(--hairline-strong);
  border-radius: var(--radius-md);
  background: var(--ink-900);
  font-family: var(--font-mono);
  font-size: 12px;
  overflow: hidden;
}
.title-block__row {
  display: flex;
  border-bottom: 1px solid var(--hairline);
}
.title-block__row:last-child { border-bottom: 0; }
.title-block__cell {
  flex: 1;
  padding: var(--sp-2) var(--sp-3);
  border-right: 1px solid var(--hairline);
}
.title-block__cell:last-child { border-right: 0; }
.title-block__label {
  display: block; color: var(--graphite); letter-spacing: 0.08em; font-size: 10px; margin-bottom: 2px;
}
.title-block__value { color: var(--paper); }
.title-block__value--accent { color: var(--marker); }

/* Breadcrumb strip, used on every inner page under the header */
.crumb-strip {
  border-bottom: 1px solid var(--hairline);
  background: var(--ink-900);
}
.crumb-strip .container { padding-top: var(--sp-3); padding-bottom: var(--sp-3); }
.crumb {
  display: flex; align-items: center; flex-wrap: wrap; gap: var(--sp-2);
  font-family: var(--font-mono); font-size: 12px; color: var(--graphite);
}
.crumb a { color: var(--graphite); }
.crumb a:hover { color: var(--blueprint); }
.crumb__sep { color: var(--graphite-dim); }
.crumb__current { color: var(--paper); }

/* -------------------------------------------------------------------- */
/* Buttons                                                               */
/* -------------------------------------------------------------------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: var(--sp-2);
  padding: 11px 20px;
  border-radius: var(--radius-md);
  font-size: 14px; font-weight: 500;
  border: 1px solid transparent;
  position: relative;
  overflow: hidden;
  transition: transform 0.12s ease, border-color 0.15s ease, background-color 0.15s ease;
}
.btn:active { transform: translateY(1px); }

.btn--primary { background: var(--marker); color: var(--ink-950); font-weight: 600; }
.btn--primary:hover { background: #ffc04d; }

.btn--ghost { background: transparent; border-color: var(--hairline-strong); color: var(--paper); }
.btn--ghost:hover { border-color: var(--blueprint); color: var(--blueprint); }

.btn--sm { padding: 7px 14px; font-size: 13px; }
.btn svg { width: 16px; height: 16px; }

/* -------------------------------------------------------------------- */
/* Cards                                                                 */
/* -------------------------------------------------------------------- */
.card {
  --accent: var(--blueprint);
  display: block;
  background: var(--ink-900);
  border: 1px solid var(--hairline);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-md);
  padding: var(--sp-5);
  transition: border-color 0.15s ease, transform 0.15s ease, box-shadow 0.15s ease;
  position: relative;
}
.card:hover {
  border-color: var(--hairline-strong);
  border-left-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: 0 12px 28px -16px rgba(0,0,0,0.6), 0 0 0 1px var(--hairline);
}

.card__index {
  font-family: var(--font-mono); font-size: 11px; color: var(--accent);
  letter-spacing: 0.06em; margin-bottom: var(--sp-3); display: block;
}
.card__title { font-family: var(--font-display); font-size: 18px; font-weight: 600; margin-bottom: var(--sp-2); }
.card__desc { color: var(--graphite); font-size: 13.5px; line-height: 1.5; }
.card__foot {
  margin-top: var(--sp-4); padding-top: var(--sp-3);
  border-top: 1px solid var(--hairline);
  display: flex; align-items: center; justify-content: space-between;
  font-family: var(--font-mono); font-size: 11px; color: var(--graphite);
}

.card__icon {
  width: 40px; height: 40px; border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  background: rgba(63, 169, 245, 0.16); /* fallback for browsers without color-mix() */
  background: color-mix(in srgb, var(--accent) 16%, transparent);
  color: var(--accent);
  margin-bottom: var(--sp-4);
}
.card__icon svg { width: 22px; height: 22px; }

/* Branch cards get their material accent inline via style="--accent:" */

.badge {
  display: inline-flex; align-items: center; gap: 5px;
  font-family: var(--font-mono); font-size: 10.5px; letter-spacing: 0.05em; text-transform: uppercase;
  padding: 3px 9px; border-radius: 100px;
  background: var(--blueprint-dim); color: var(--blueprint);
  border: 1px solid rgba(63,169,245,0.3);
}
.badge--marker { background: var(--marker-dim); color: var(--marker); border-color: rgba(255,176,32,0.3); }

/* -------------------------------------------------------------------- */
/* Resource-type chooser (Notes / PYQ / Practical)                      */
/* -------------------------------------------------------------------- */
.resource-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--sp-5);
}
.resource-card {
  --accent: var(--blueprint);
  text-align: left;
  background: linear-gradient(180deg, var(--ink-900), var(--ink-850));
  border: 1px solid var(--hairline);
  border-radius: var(--radius-lg);
  padding: var(--sp-6) var(--sp-5);
}
.resource-card:hover { border-color: var(--accent); }
.resource-card .card__icon { width: 52px; height: 52px; margin-bottom: var(--sp-5); }
.resource-card .card__icon svg { width: 26px; height: 26px; }
.resource-card h3 { font-size: 21px; margin-bottom: var(--sp-2); }
.resource-card p { color: var(--graphite); font-size: 13.5px; }

/* -------------------------------------------------------------------- */
/* Document register — the PDF listing, styled like a drawing log       */
/* -------------------------------------------------------------------- */
.register { border: 1px solid var(--hairline); border-radius: var(--radius-md); overflow: hidden; }
.register__head, .register-row {
  display: grid;
  grid-template-columns: 1fr 110px 140px 90px;
  gap: var(--sp-3);
  align-items: center;
  padding: var(--sp-3) var(--sp-4);
}
.register__head {
  font-family: var(--font-mono); font-size: 10.5px; letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--graphite); background: var(--ink-900); border-bottom: 1px solid var(--hairline);
}
.register-row {
  background: var(--ink-950);
  border-bottom: 1px solid var(--hairline);
  transition: background-color 0.12s ease;
}
.register-row:last-child { border-bottom: 0; }
.register-row:hover { background: var(--ink-900); }
.register-row__name { display: flex; align-items: center; gap: var(--sp-3); font-size: 14.5px; min-width: 0; }
.register-row__name svg { flex-shrink: 0; width: 18px; height: 18px; color: var(--blueprint); }
.register-row__name span { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.register-row__size, .register-row__date { font-family: var(--font-mono); font-size: 12.5px; color: var(--graphite); }
.register-row__actions { display: flex; gap: var(--sp-2); justify-content: flex-end; }
.register-row__actions a { color: var(--graphite); }
.register-row__actions a:hover { color: var(--marker); }
.register-row__actions svg { width: 18px; height: 18px; }

/* -------------------------------------------------------------------- */
/* Empty / error states — a redline correction mark                     */
/* -------------------------------------------------------------------- */
.empty-state {
  text-align: center;
  padding: var(--sp-8) var(--sp-5);
  border: 1px dashed var(--hairline-strong);
  border-radius: var(--radius-lg);
  color: var(--graphite);
}
.empty-state svg { width: 40px; height: 40px; color: var(--graphite-dim); margin: 0 auto var(--sp-4); }
.empty-state h3 { color: var(--paper); font-size: 17px; margin-bottom: var(--sp-2); }
.empty-state p { font-size: 13.5px; max-width: 420px; margin: 0 auto; }

.error-state { border-color: rgba(255,93,93,0.35); }
.error-state svg { color: var(--redline); }

/* -------------------------------------------------------------------- */
/* Skeleton loading                                                     */
/* -------------------------------------------------------------------- */
.skeleton {
  background: linear-gradient(90deg, var(--ink-900) 25%, var(--ink-800) 37%, var(--ink-900) 63%);
  background-size: 400% 100%;
  animation: shimmer 1.4s ease infinite;
  border-radius: var(--radius-sm);
}

/* -------------------------------------------------------------------- */
/* Hero (index.html)                                                    */
/* -------------------------------------------------------------------- */
.hero { padding: var(--sp-9) 0 var(--sp-8); position: relative; }
.hero__kicker { margin-bottom: var(--sp-4); }
.hero h1 {
  font-size: clamp(34px, 5.4vw, 60px);
  line-height: 1.05;
  max-width: 16ch;
  margin-bottom: var(--sp-5);
}
.hero h1 em {
  font-style: normal; color: var(--blueprint);
}
.hero p.lede { font-size: 17px; color: var(--paper-dim); max-width: 52ch; margin-bottom: var(--sp-6); }
.hero__actions { display: flex; gap: var(--sp-3); flex-wrap: wrap; margin-bottom: var(--sp-8); }

.hero__block {
  display: grid; grid-template-columns: 1.3fr 1fr; gap: var(--sp-7);
  align-items: end;
}
.hero__titleblock-wrap { display: flex; justify-content: flex-end; }
.hero__titleblock-wrap .title-block { width: 100%; max-width: 320px; }

.stat-strip { display: flex; gap: var(--sp-7); margin-top: var(--sp-7); flex-wrap: wrap; }
.stat-strip__item { font-family: var(--font-mono); }
.stat-strip__num { font-size: 26px; color: var(--paper); display: block; font-weight: 600; }
.stat-strip__label { font-size: 11px; color: var(--graphite); letter-spacing: 0.06em; text-transform: uppercase; }

/* -------------------------------------------------------------------- */
/* Search page                                                          */
/* -------------------------------------------------------------------- */
.search-hero { padding: var(--sp-7) 0 var(--sp-5); }
.search-box-lg {
  display: flex; align-items: center; gap: var(--sp-3);
  border: 1px solid var(--hairline-strong); background: var(--ink-900);
  border-radius: var(--radius-md); padding: var(--sp-4) var(--sp-5);
}
.search-box-lg:focus-within { border-color: var(--blueprint); }
.search-box-lg input { flex: 1; background: none; border: 0; outline: none; color: var(--paper); font-size: 16px; }
.search-box-lg svg { width: 20px; height: 20px; color: var(--graphite); flex-shrink: 0; }

.search-group { margin-bottom: var(--sp-6); }
.search-group__label {
  font-family: var(--font-mono); font-size: 11px; text-transform: uppercase; letter-spacing: 0.08em;
  color: var(--graphite); margin-bottom: var(--sp-3);
}
.search-result-row {
  display: flex; align-items: center; justify-content: space-between; gap: var(--sp-4);
  padding: var(--sp-3) var(--sp-4);
  border: 1px solid var(--hairline);
  border-radius: var(--radius-sm);
  margin-bottom: var(--sp-2);
}
.search-result-row:hover { border-color: var(--blueprint); }
.search-result-row__path { font-family: var(--font-mono); font-size: 11px; color: var(--graphite); margin-top: 2px; }

/* -------------------------------------------------------------------- */
/* Footer                                                                */
/* -------------------------------------------------------------------- */
.site-footer {
  border-top: 1px solid var(--hairline);
  padding: var(--sp-6) 0;
  margin-top: var(--sp-9);
}
.site-footer .container { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: var(--sp-3); }
.site-footer p { font-size: 12.5px; color: var(--graphite); font-family: var(--font-mono); }

/* -------------------------------------------------------------------- */
/* 404                                                                   */
/* -------------------------------------------------------------------- */
.not-found { text-align: center; padding: var(--sp-9) 0; }
.not-found .stamp {
  display: inline-block; font-family: var(--font-mono); font-size: 100px; font-weight: 700;
  color: transparent; -webkit-text-stroke: 2px var(--redline); letter-spacing: 0.02em;
}