/* ============================================
   contrapaul.com/edu — education resources
   Clean, structured, utilitarian-precise.
   Light neutral palette. High legibility.
   ============================================ */

:root {
  --bg:         #f8f9fa;
  --surface:    #ffffff;
  --surface-2:  #f0f2f4;
  --border:     #dde1e6;
  --border-strong: #b0b8c4;
  --text:       #111418;
  --muted:      #64748b;
  --accent:     #1a5cb8;    /* academic blue */
  --accent-bg:  #eef3fb;
  --hl:         #7c3aed;    /* HL purple */
  --hl-bg:      #f3eeff;
  --green:      #166534;
  --green-bg:   #dcfce7;
  --amber:      #92400e;
  --amber-bg:   #fef3c7;
  --font-display: "Georgia", "Times New Roman", serif;
  --font-body:    "Helvetica Neue", Helvetica, Arial, sans-serif;
  --font-mono:    "Courier New", Courier, monospace;
  --max-w:        1100px;
  --radius:       6px;
  --transition:   160ms ease;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; background: var(--bg); }
body { font-family: var(--font-body); line-height: 1.6; color: var(--text); -webkit-font-smoothing: antialiased; display: flex; flex-direction: column; min-height: 100vh; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
img { display: block; max-width: 100%; }
main { flex: 1; }

/* --- HEADER --- */
.site-header {
  background: var(--surface);
  border-bottom: 2px solid var(--accent);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 2rem;
  height: 54px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.wordmark {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--text);
  font-weight: bold;
  text-decoration: none;
  letter-spacing: 0.02em;
}
.brand-sub { color: var(--accent); font-weight: normal; }
.wordmark:hover { text-decoration: none; }

.nav { display: flex; align-items: center; gap: 0.1rem; }
.nav a {
  font-size: 0.83rem;
  padding: 0.35rem 0.8rem;
  color: var(--muted);
  border-radius: var(--radius);
  transition: background var(--transition), color var(--transition);
  text-decoration: none;
}
.nav a:hover { background: var(--surface-2); color: var(--text); }
.nav-external {
  border-left: 1px solid var(--border);
  margin-left: 0.5rem;
  padding-left: 1rem !important;
  font-family: var(--font-mono);
  font-size: 0.75rem !important;
}

/* --- HERO --- */
.hero {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 4.5rem 2rem;
}

.hero-inner { max-width: var(--max-w); margin: 0 auto; }

.hero-badge {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-bg);
  border: 1px solid #b8d0f0;
  padding: 0.3rem 0.8rem;
  border-radius: 2px;
  margin-bottom: 1.5rem;
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 400;
  line-height: 1.2;
  letter-spacing: -0.01em;
  margin-bottom: 1.25rem;
  max-width: 22ch;
}

.hero-sub {
  font-size: 1.05rem;
  color: var(--muted);
  max-width: 58ch;
  line-height: 1.7;
  margin-bottom: 2rem;
}

.hero-actions { display: flex; gap: 0.75rem; flex-wrap: wrap; margin-bottom: 3rem; }

.btn-primary {
  display: inline-block;
  padding: 0.65rem 1.5rem;
  background: var(--accent);
  color: #fff;
  font-size: 0.88rem;
  border-radius: var(--radius);
  font-weight: 500;
  transition: background var(--transition);
  text-decoration: none;
}
.btn-primary:hover { background: #1448a0; text-decoration: none; }

.btn-ghost {
  display: inline-block;
  padding: 0.65rem 1.5rem;
  border: 1px solid var(--border-strong);
  color: var(--muted);
  font-size: 0.88rem;
  border-radius: var(--radius);
  transition: border-color var(--transition), color var(--transition);
  text-decoration: none;
}
.btn-ghost:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }

.hero-stats {
  display: flex;
  align-items: center;
  gap: 2rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}

.stat { display: flex; flex-direction: column; gap: 0.15rem; }
.stat-n { font-family: var(--font-display); font-size: 1.4rem; color: var(--text); }
.stat-label { font-size: 0.72rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.08em; font-family: var(--font-mono); }
.stat-divider { width: 1px; height: 36px; background: var(--border); }

/* --- SHARED --- */
.section-inner { max-width: var(--max-w); margin: 0 auto; padding: 4.5rem 2rem; }

.section-header { margin-bottom: 2.5rem; }

.section-title {
  font-family: var(--font-display);
  font-size: 1.6rem;
  font-weight: 400;
  margin-bottom: 0.5rem;
}

.section-desc { font-size: 0.95rem; color: var(--muted); max-width: 60ch; }

/* --- UNITS --- */
.units { border-bottom: 1px solid var(--border); }

.units-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.25rem;
}

.unit-card {
  display: flex;
  flex-direction: column;
  padding: 1.5rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color var(--transition), box-shadow var(--transition);
  text-decoration: none;
  color: var(--text);
}
.unit-card:hover {
  border-color: var(--accent);
  box-shadow: 0 2px 12px rgba(26, 92, 184, 0.08);
  text-decoration: none;
}
.unit-card.unit-hl { border-left: 3px solid var(--hl); }
.unit-card.unit-hl:hover { border-color: var(--hl); box-shadow: 0 2px 12px rgba(124, 58, 237, 0.08); }

.unit-code {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.6rem;
}

.unit-title {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 400;
  margin-bottom: 0.6rem;
  line-height: 1.35;
}

.unit-desc { font-size: 0.85rem; color: var(--muted); line-height: 1.6; flex: 1; margin-bottom: 1.25rem; }

.unit-footer { display: flex; justify-content: space-between; align-items: center; }

.unit-tag {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.2rem 0.6rem;
  background: var(--accent-bg);
  color: var(--accent);
  border-radius: 2px;
}
.unit-tag-hl {
  background: var(--hl-bg);
  color: var(--hl);
}

.unit-arrow { font-size: 1rem; color: var(--border-strong); transition: transform var(--transition), color var(--transition); }
.unit-card:hover .unit-arrow { transform: translateX(4px); color: var(--accent); }
.unit-card.unit-hl:hover .unit-arrow { color: var(--hl); }

/* --- TOOLS --- */
.tools { background: var(--surface-2); border-bottom: 1px solid var(--border); }

.tools-list { display: flex; flex-direction: column; gap: 0; }

.tool-row {
  display: grid;
  grid-template-columns: 48px 1fr auto;
  gap: 1.25rem;
  align-items: center;
  padding: 1.5rem 1.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 0.75rem;
  text-decoration: none;
  color: var(--text);
  transition: border-color var(--transition), box-shadow var(--transition);
}
.tool-row:last-child { margin-bottom: 0; }
.tool-row:hover { border-color: var(--accent); box-shadow: 0 1px 8px rgba(26,92,184,0.07); text-decoration: none; }

.tool-icon { font-size: 1.5rem; text-align: center; }

.tool-body h3 { font-size: 1rem; margin-bottom: 0.3rem; }
.tool-body p { font-size: 0.85rem; color: var(--muted); }

.tool-status {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.25rem 0.6rem;
  border-radius: 2px;
  white-space: nowrap;
}
.tool-ready { background: var(--green-bg); color: var(--green); }
.tool-wip { background: var(--amber-bg); color: var(--amber); }

/* --- ABOUT STRIP --- */
.about-strip { border-bottom: 1px solid var(--border); }
.about-inner {
  display: grid;
  grid-template-columns: 1fr 380px;
  gap: 4rem;
  align-items: start;
}

.about-text-col .section-title { margin-bottom: 1rem; }
.about-text-col p { font-size: 0.95rem; color: var(--muted); line-height: 1.75; margin-bottom: 1rem; }

.contact-link {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--accent);
  letter-spacing: 0.04em;
}

.note-card {
  background: var(--accent-bg);
  border: 1px solid #b8d0f0;
  border-radius: var(--radius);
  padding: 1.5rem;
}

.note-label {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.75rem;
}

.note-card p { font-size: 0.875rem; color: #334d80; line-height: 1.7; }

/* --- FOOTER --- */
.site-footer { padding: 1.25rem 2rem; border-top: 1px solid var(--border); background: var(--surface); }
.footer-inner { max-width: var(--max-w); margin: 0 auto; display: flex; justify-content: space-between; align-items: center; }
.footer-brand { font-family: var(--font-mono); font-size: 0.75rem; color: var(--text); }
.footer-note { font-size: 0.72rem; color: var(--muted); }

/* --- RESPONSIVE --- */
@media (max-width: 800px) {
  .about-inner { grid-template-columns: 1fr; gap: 2rem; }
}
@media (max-width: 600px) {
  .tool-row { grid-template-columns: 40px 1fr; }
  .tool-status { display: none; }
  .hero-stats { gap: 1.25rem; }
  .stat-divider { display: none; }
}
@media (max-width: 480px) {
  .section-inner { padding: 3rem 1.25rem; }
  .hero { padding: 3rem 1.25rem; }
  .header-inner { padding: 0 1.25rem; }
  .nav a { padding: 0.3rem 0.5rem; font-size: 0.78rem; }
  .nav-external { display: none; }
}