/* ============================================================
   Study Stack — design tokens
   Concept: a student's ruled notebook / index-card study system.
   ============================================================ */

:root {
  --paper: #F5EFE0;
  --paper-line: #E3D9BE;
  --ink: #23241F;
  --ink-soft: #5B5748;
  --margin-red: #B8433B;
  --highlighter: #FFD23F;
  --teal: #26666D;
  --teal-dark: #1B4A50;
  --card-shadow: rgba(35, 36, 31, 0.18);

  --font-display: "Space Mono", "Courier New", monospace;
  --font-body: "Work Sans", "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  background-image: repeating-linear-gradient(
    to bottom,
    transparent,
    transparent 34px,
    var(--paper-line) 34px,
    var(--paper-line) 35px
  );
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--teal-dark); }
a:hover { color: var(--margin-red); }

.wrap {
  max-width: 880px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- Binder tab nav ---------- */

.site-nav {
  background: var(--ink);
  padding: 14px 0;
  position: sticky;
  top: 0;
  z-index: 20;
}

.site-nav .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

.brand {
  font-family: var(--font-display);
  color: var(--paper);
  font-size: 1.1rem;
  text-decoration: none;
  letter-spacing: 0.5px;
}

.brand span { color: var(--highlighter); }

.tabs {
  display: flex;
  gap: 6px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.tabs a {
  display: inline-block;
  font-family: var(--font-display);
  font-size: 0.8rem;
  color: var(--paper);
  text-decoration: none;
  padding: 8px 14px;
  background: var(--teal-dark);
  border-radius: 6px 6px 0 0;
  transition: background 0.15s ease, transform 0.15s ease;
}

.tabs a:hover, .tabs a.active {
  background: var(--margin-red);
  transform: translateY(-2px);
}

/* ---------- Margin rule (signature element) ---------- */

.page {
  position: relative;
  padding-left: 56px;
  border-left: 3px solid var(--margin-red);
  margin: 48px 24px 80px 40px;
}

@media (max-width: 640px) {
  .page { padding-left: 28px; margin-left: 16px; }
}

.page::before {
  content: "";
  position: absolute;
  left: -3px;
  top: 0;
  bottom: 0;
  width: 3px;
  background: var(--margin-red);
}

/* punch holes */
.punch {
  position: absolute;
  left: -66px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--paper);
  box-shadow: inset 0 0 0 2px var(--paper-line), 0 0 0 2px var(--paper) ;
  border: 2px solid var(--ink-soft);
}
@media (max-width: 640px) { .punch { display: none; } }
.punch.p1 { top: 40px; }
.punch.p2 { top: 50%; }
.punch.p3 { bottom: 40px; }

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

.hero {
  padding: 20px 0 10px;
}

.hero .eyebrow {
  font-family: var(--font-display);
  font-size: 0.8rem;
  color: var(--margin-red);
  text-transform: uppercase;
  letter-spacing: 1.5px;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 3.1rem);
  line-height: 1.15;
  margin: 10px 0 18px;
}

.hero h1 mark {
  background: var(--highlighter);
  color: var(--ink);
  padding: 0 6px;
}

.hero p.lede {
  max-width: 60ch;
  color: var(--ink-soft);
  font-size: 1.05rem;
}

.cta-row { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 22px; }

.btn {
  font-family: var(--font-display);
  font-size: 0.85rem;
  text-decoration: none;
  display: inline-block;
  padding: 12px 20px;
  border-radius: 4px;
  border: 2px solid var(--ink);
  color: var(--ink);
  background: transparent;
  transition: all 0.15s ease;
}

.btn.solid {
  background: var(--ink);
  color: var(--paper);
}

.btn:hover {
  background: var(--margin-red);
  border-color: var(--margin-red);
  color: #fff;
}

/* ---------- Index cards (post grid) ---------- */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 26px;
  margin: 30px 0;
}

.card {
  background: #FFFEF9;
  border: 1px solid var(--paper-line);
  border-radius: 3px;
  padding: 20px;
  box-shadow: 4px 4px 0 var(--card-shadow);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  text-decoration: none;
  color: var(--ink);
  display: block;
  transform: rotate(var(--tilt, 0deg));
}

.card:nth-child(3n+1) { --tilt: -1deg; }
.card:nth-child(3n+2) { --tilt: 0.6deg; }
.card:nth-child(3n)   { --tilt: -0.4deg; }

.card:hover {
  transform: rotate(0deg) translateY(-4px);
  box-shadow: 6px 8px 0 var(--card-shadow);
}

.card .tag {
  display: inline-block;
  font-family: var(--font-display);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  background: var(--highlighter);
  padding: 3px 8px;
  border-radius: 3px;
  margin-bottom: 10px;
}

.card h3 {
  font-family: var(--font-display);
  font-size: 1.05rem;
  margin: 0 0 8px;
  line-height: 1.3;
}

.card p { color: var(--ink-soft); font-size: 0.92rem; margin: 0; }

/* ---------- Article ---------- */

article h1 {
  font-family: var(--font-display);
  font-size: clamp(1.7rem, 4vw, 2.4rem);
  line-height: 1.2;
}

article .meta {
  font-family: var(--font-display);
  font-size: 0.78rem;
  color: var(--ink-soft);
  margin-bottom: 26px;
}

article h2 {
  font-family: var(--font-display);
  font-size: 1.25rem;
  margin-top: 36px;
  border-bottom: 2px solid var(--ink);
  display: inline-block;
  padding-bottom: 3px;
}

article p { max-width: 68ch; }

.margin-note {
  background: #FFFBEA;
  border-left: 4px solid var(--highlighter);
  padding: 14px 18px;
  margin: 22px 0;
  font-size: 0.95rem;
  max-width: 60ch;
}

.margin-note strong { color: var(--margin-red); }

.affiliate-box {
  background: var(--teal);
  color: #fff;
  padding: 18px 22px;
  border-radius: 6px;
  margin: 26px 0;
  max-width: 60ch;
}

.affiliate-box a {
  color: var(--highlighter);
  font-weight: 600;
}

.disclosure-note {
  font-size: 0.8rem;
  color: var(--ink-soft);
  border-top: 1px dashed var(--paper-line);
  margin-top: 50px;
  padding-top: 14px;
}

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

footer {
  background: var(--ink);
  color: var(--paper);
  padding: 30px 0;
  margin-top: 60px;
}

footer .wrap {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  font-family: var(--font-display);
  font-size: 0.78rem;
}

footer a { color: var(--highlighter); }

/* ---------- utility ---------- */

.list-plain { padding-left: 20px; }
.list-plain li { margin-bottom: 8px; }