/* ---------------------------------------------------------------------------
   Matrix Theory and Applications I -- site styles
   One stylesheet, no framework, no build step. Light and dark.
   --------------------------------------------------------------------------- */

:root {
  --bg:        #ffffff;
  --bg-soft:   #f6f7f9;
  --bg-sunken: #eceff3;
  --fg:        #1a1d21;
  --fg-muted:  #5b6470;
  --fg-faint:  #858e9a;
  --rule:      #dde1e7;
  --accent:    #1f4e8c;
  --accent-fg: #ffffff;
  --accent-soft: #e8eef7;
  --mark:      #b4531a;
  --radius: 8px;
  --measure: 74ch;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:        #14171b;
    --bg-soft:   #1b1f25;
    --bg-sunken: #21262e;
    --fg:        #e6e9ed;
    --fg-muted:  #a3adba;
    --fg-faint:  #7d8794;
    --rule:      #2c333c;
    --accent:    #7aa8e0;
    --accent-fg: #14171b;
    --accent-soft: #1d2836;
    --mark:      #e0975f;
  }
}

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

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
        "Helvetica Neue", Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

/* --- Header and navigation ------------------------------------------------ */

.site-header {
  background: var(--accent);
  color: var(--accent-fg);
  border-bottom: 1px solid var(--rule);
}

.site-header__inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1.1rem 1.25rem 0.9rem;
}

.site-title {
  display: block;
  font-size: 1.28rem;
  font-weight: 650;
  letter-spacing: -0.01em;
  color: var(--accent-fg);
  text-decoration: none;
}

.site-tagline {
  margin: 0.2rem 0 0;
  font-size: 0.9rem;
  opacity: 0.82;
}

.site-nav {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 1.25rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.15rem;
}

.site-nav a {
  display: inline-block;
  padding: 0.55rem 0.85rem;
  color: var(--accent-fg);
  text-decoration: none;
  font-size: 0.92rem;
  opacity: 0.85;
  border-bottom: 2px solid transparent;
}

.site-nav a:hover { opacity: 1; }
.site-nav a.is-active {
  opacity: 1;
  font-weight: 600;
  border-bottom-color: var(--accent-fg);
}

/* In dark mode the accent inverts to a light blue, which as a full-width
   header band is uncomfortably bright. Use a recessed bar instead. */
@media (prefers-color-scheme: dark) {
  .site-header { background: var(--bg-soft); color: var(--fg); }
  .site-title  { color: var(--fg); }
  .site-nav a  { color: var(--fg-muted); }
  .site-nav a:hover { color: var(--fg); }
  .site-nav a.is-active { color: var(--accent); border-bottom-color: var(--accent); }
}

/* --- Layout --------------------------------------------------------------- */

.wrap {
  max-width: 1080px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

.prose { max-width: var(--measure); }

h1, h2, h3, h4 {
  line-height: 1.25;
  letter-spacing: -0.012em;
  margin: 2rem 0 0.6rem;
}

h1 { font-size: 1.85rem; margin-top: 0.5rem; }
h2 { font-size: 1.32rem; padding-top: 0.6rem; border-top: 1px solid var(--rule); }
h3 { font-size: 1.06rem; color: var(--fg-muted); }

p, ul, ol { margin: 0.7rem 0; }
li { margin: 0.28rem 0; }

a { color: var(--accent); text-underline-offset: 2px; }
a:hover { text-decoration-thickness: 2px; }

hr { border: 0; border-top: 1px solid var(--rule); margin: 2rem 0; }

code {
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  font-size: 0.88em;
  background: var(--bg-sunken);
  padding: 0.12em 0.36em;
  border-radius: 4px;
}

pre {
  background: var(--bg-sunken);
  padding: 0.9rem 1rem;
  border-radius: var(--radius);
  overflow-x: auto;
}
pre code { background: none; padding: 0; }

blockquote {
  margin: 1rem 0;
  padding: 0.1rem 0 0.1rem 1rem;
  border-left: 3px solid var(--accent);
  color: var(--fg-muted);
}

/* --- Hero ----------------------------------------------------------------- */

.hero {
  background: var(--bg-soft);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1.4rem 1.5rem;
  margin-bottom: 1.6rem;
}
.hero p:first-child { margin-top: 0; }
.hero p:last-child { margin-bottom: 0; }

/* --- Fact grid ------------------------------------------------------------ */

.facts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 0.75rem;
  margin: 1.2rem 0 1.8rem;
  padding: 0;
  list-style: none;
}

.facts li {
  background: var(--bg-soft);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 0.75rem 0.9rem;
  margin: 0;
}

.facts .k {
  display: block;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-faint);
}

.facts .v { font-weight: 600; }

/* --- Cards ---------------------------------------------------------------- */

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 0.9rem;
  margin: 1.2rem 0;
  padding: 0;
  list-style: none;
}

.card {
  display: block;
  background: var(--bg-soft);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 0.95rem 1.1rem;
  text-decoration: none;
  color: inherit;
  transition: border-color .12s ease, transform .12s ease;
}
.card:hover { border-color: var(--accent); transform: translateY(-1px); }
.card strong { display: block; color: var(--accent); margin-bottom: 0.2rem; }
.card span { font-size: 0.9rem; color: var(--fg-muted); }

/* --- Tables --------------------------------------------------------------- */

.table-scroll { overflow-x: auto; margin: 1rem 0; }

table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.92rem;
}

th, td {
  text-align: left;
  padding: 0.55rem 0.7rem;
  border-bottom: 1px solid var(--rule);
  vertical-align: top;
}

thead th {
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-faint);
  border-bottom: 2px solid var(--rule);
  white-space: nowrap;
}

tbody tr:hover { background: var(--bg-soft); }

td.num, th.num { text-align: right; white-space: nowrap; }

.part-row td {
  background: var(--accent-soft);
  font-weight: 650;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
}

/* --- Badges --------------------------------------------------------------- */

.badge {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.12rem 0.45rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  white-space: nowrap;
}
.badge--mark { background: transparent; color: var(--mark); border: 1px solid var(--mark); }

/* --- Week page ------------------------------------------------------------ */

.week-head {
  display: flex;
  align-items: baseline;
  gap: 0.7rem;
  flex-wrap: wrap;
  margin-bottom: 0.2rem;
}
.week-head .eyebrow {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--fg-faint);
}

.materials {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
  gap: 0.75rem;
  padding: 0;
  list-style: none;
  margin: 1rem 0;
}
.materials li {
  border: 1px dashed var(--rule);
  border-radius: var(--radius);
  padding: 0.7rem 0.9rem;
  margin: 0;
  font-size: 0.9rem;
}
.materials .pending { color: var(--fg-faint); font-style: italic; }

.pager {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--rule);
  font-size: 0.92rem;
}

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

.site-footer {
  border-top: 1px solid var(--rule);
  background: var(--bg-soft);
  color: var(--fg-muted);
  font-size: 0.86rem;
}
.site-footer .wrap { padding: 1.5rem 1.25rem; }

@media (max-width: 640px) {
  h1 { font-size: 1.5rem; }
  .wrap { padding: 1.5rem 1rem 3rem; }
}