/* ---------- PrepZ — shared site styles ---------- */

:root {
  --ink: #14181f;
  --paper: #fafaf8;
  --card: #ffffff;
  --line: #e6e4de;
  --muted: #6b7178;

  --physics: #2f6fed;   /* blue  */
  --chem:    #1f9e6d;   /* green */
  --bio:     #0d9488;   /* teal  */
  --accent:  #14181f;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

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

/* ---------- header ---------- */

header.site {
  border-bottom: 1px solid var(--line);
  background: var(--paper);
  position: sticky;
  top: 0;
  z-index: 10;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 0;
}

.logo {
  display: flex;
  align-items: baseline;
  gap: 8px;
  font-weight: 800;
  font-size: 1.25rem;
  text-decoration: none;
  letter-spacing: -0.01em;
}

.logo .dot-p { color: var(--physics); }
.logo .dot-c { color: var(--chem); }
.logo .dot-b { color: var(--bio); }

.logo small {
  font-weight: 500;
  font-size: 0.72rem;
  color: var(--muted);
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

nav.links {
  display: flex;
  gap: 26px;
  font-size: 0.92rem;
  font-weight: 500;
}

nav.links a {
  text-decoration: none;
  color: var(--muted);
  transition: color 0.15s ease;
}

nav.links a:hover,
nav.links a.active {
  color: var(--ink);
}

@media (max-width: 640px) {
  nav.links { display: none; }
}

/* ---------- hero ---------- */

.hero {
  padding: 72px 0 48px;
}

.hero .eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 18px;
}

.hero .eyebrow .chip {
  display: inline-block;
  width: 8px; height: 8px;
  border-radius: 2px;
  background: var(--bio);
}

h1 {
  font-size: clamp(2rem, 4.5vw, 3.1rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
  margin: 0 0 18px;
  font-weight: 800;
}

.hero p.lede {
  font-size: 1.15rem;
  color: var(--muted);
  max-width: 60ch;
  margin: 0 0 30px;
}

.subject-rule {
  display: flex;
  height: 4px;
  width: 220px;
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 34px;
}
.subject-rule span { flex: 1; }
.subject-rule .p { background: var(--physics); }
.subject-rule .c { background: var(--chem); }
.subject-rule .b { background: var(--bio); }

/* ---------- cards / sections ---------- */

.section { padding: 40px 0; }
.section + .section { border-top: 1px solid var(--line); }

h2 {
  font-size: 1.5rem;
  letter-spacing: -0.01em;
  margin: 0 0 14px;
}

h3 {
  font-size: 1.05rem;
  margin: 24px 0 8px;
}

p { margin: 0 0 14px; color: #2a2f37; }

.grid3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 24px;
}

@media (max-width: 640px) {
  .grid3 { grid-template-columns: 1fr; }
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 22px;
}

.card .tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 3px 8px;
  border-radius: 5px;
  margin-bottom: 12px;
  color: #fff;
}
.card.physics .tag { background: var(--physics); }
.card.chem .tag { background: var(--chem); }
.card.bio .tag { background: var(--bio); }

.card h3 { margin-top: 0; }
.card p { color: var(--muted); font-size: 0.94rem; margin-bottom: 0; }

/* ---------- buttons ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--ink);
  color: #fff;
  text-decoration: none;
  padding: 12px 22px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  transition: opacity 0.15s ease;
}
.btn:hover { opacity: 0.85; }

.btn.ghost {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--line);
}

/* ---------- legal pages ---------- */

.legal h1 { font-size: 2rem; margin-bottom: 6px; }
.legal .updated { color: var(--muted); font-size: 0.88rem; margin-bottom: 34px; }
.legal ul { padding-left: 20px; color: #2a2f37; }
.legal li { margin-bottom: 8px; }

/* ---------- footer ---------- */

footer.site {
  border-top: 1px solid var(--line);
  margin-top: 60px;
  padding: 34px 0 48px;
  color: var(--muted);
  font-size: 0.88rem;
}

footer.site .foot-links {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  margin-bottom: 16px;
}

footer.site a { text-decoration: none; color: var(--muted); }
footer.site a:hover { color: var(--ink); }