/* ---------------------------------------------------------------------------
   Babak Shahbaba — personal site
   Plain, dependency-free stylesheet
   --------------------------------------------------------------------------- */

:root {
  --bg:        #fbfaf7;
  --surface:   #ffffff;
  --text:      #1c1e21;
  --muted:     #5b6470;
  --border:    #e7e3da;
  --accent:    #1b4b7a;
  --accent-2:  #2f6db0;
  --tag-bg:    #eef2f6;
  --maxw:      1060px;
  --radius:    10px;
  --shadow:    0 1px 2px rgba(20,30,45,.05), 0 6px 24px rgba(20,30,45,.05);
  --serif:     "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, serif;
  --sans:      -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:      #14161a;
    --surface: #1c1f24;
    --text:    #e7e8ea;
    --muted:   #9aa3af;
    --border:  #2c313a;
    --accent:  #7db2e6;
    --accent-2:#a9cdf0;
    --tag-bg:  #232833;
    --shadow:  0 1px 2px rgba(0,0,0,.3), 0 6px 24px rgba(0,0,0,.35);
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3 { font-family: var(--serif); font-weight: 600; line-height: 1.25; }

/* ---------- layout ---------- */
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

section { padding: 56px 0; border-top: 1px solid var(--border); }
section:first-of-type { border-top: 0; }
section h2 {
  font-size: 1.6rem;
  margin: 0 0 6px;
}
section > .wrap > .lead { color: var(--muted); margin-top: 0; }

/* ---------- header / nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(8px);
  border-bottom: 1px solid var(--border);
}
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 12px 24px;
}
.brand {
  font-family: var(--serif);
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--text);
  letter-spacing: .2px;
}
.brand:hover { text-decoration: none; }
.nav-links { display: flex; gap: 26px; align-items: center; }
.nav-links a {
  color: var(--muted);
  font-size: .95rem;
  padding: 4px 0;
  border-bottom: 2px solid transparent;
}
.nav-links a:hover { color: var(--text); text-decoration: none; }
.nav-links a.active { color: var(--text); border-bottom-color: var(--accent); }

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 9px;
  cursor: pointer;
  color: var(--text);
  font-size: 1rem;
}

@media (max-width: 720px) {
  .nav-toggle { display: block; }
  .nav-links {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 8px 24px 16px;
    display: none;
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 10px 0; width: 100%; border-bottom: 1px solid var(--border); }
  .nav-links a.active { border-bottom-color: var(--border); padding-left: 6px; border-left: 3px solid var(--accent); }
}

/* ---------- hero ---------- */
.hero { padding: 60px 0 20px; border-top: 0; }
.hero-grid {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 48px;
  align-items: center;
}
.hero h1 { font-size: 2.4rem; margin: 0 0 10px; }
.hero .title { color: var(--muted); font-size: 1.1rem; margin: 0 0 20px; }
.hero p { margin: 0 0 18px; }
.hero-photo {
  width: 100%;
  height: auto;
  display: block;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.tags { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 6px; }
.tag {
  background: var(--tag-bg);
  color: var(--muted);
  font-size: .82rem;
  padding: 4px 11px;
  border-radius: 999px;
  border: 1px solid var(--border);
}
.hero-links { display: flex; flex-wrap: wrap; gap: 18px; margin-top: 22px; font-size: .95rem; }

@media (max-width: 800px) {
  .hero-grid { grid-template-columns: 1fr; gap: 28px; }
  .hero-photo { max-width: 260px; }
  .hero h1 { font-size: 2rem; }
}

/* ---------- generic content ---------- */
.prose p { margin: 0 0 16px; }
.prose h2 {
  font-size: 1.6rem;
  margin: 48px 0 14px;
  color: var(--text);
}
.prose h2:first-child { margin-top: 0; }

.subhead {
  font-family: var(--sans);
  text-transform: uppercase;
  letter-spacing: .12em;
  font-size: .78rem;
  font-weight: 600;
  color: var(--accent-2);
  margin: 40px 0 14px;
}
.subhead:first-child { margin-top: 0; }

/* ---------- cards ---------- */
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 8px; }
@media (max-width: 860px) { .cards { grid-template-columns: 1fr; } }
.card {
  background: var(--tag-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 22px 24px;
}
.card h3 { margin: 0 0 8px; font-size: 1.15rem; }
.card p { margin: 0 0 12px; color: var(--muted); font-size: .95rem; }
.card a.more { font-size: .9rem; font-weight: 600; }

/* ---------- topic blocks ---------- */
.topic { margin: 0 0 30px; }
.topic h3 { margin: 0 0 6px; font-size: 1.2rem; }
.topic p { margin: 0; }

/* ---------- lists ---------- */
.entry {
  padding: 14px 0;
  border-bottom: 1px solid var(--border);
}
.entry:last-child { border-bottom: 0; }
.entry .role, .entry .venue { color: var(--muted); font-size: .92rem; }
.pub-list { margin: 0; padding: 0; list-style: none; }
.pub-list li {
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  font-size: .97rem;
}
.pub-list li:last-child { border-bottom: 0; }
.pub-list em { color: var(--muted); font-style: italic; }

.two-col { columns: 2; column-gap: 44px; }
.two-col .entry { break-inside: avoid; }
@media (max-width: 720px) { .two-col { columns: 1; } }

/* ---------- course / code items ---------- */
.item { padding: 18px 0; border-bottom: 1px solid var(--border); }
.item:last-child { border-bottom: 0; }
.item h3 { margin: 0 0 4px; font-size: 1.1rem; }
.item p { margin: 0 0 8px; color: var(--muted); font-size: .95rem; }
.item .links { display: flex; flex-wrap: wrap; gap: 16px; font-size: .9rem; }

/* ---------- callout ---------- */
.callout {
  background: var(--tag-bg);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 22px 0;
  font-size: .96rem;
}
.callout h3 { margin: 0 0 8px; font-size: 1.05rem; }
.callout p { margin: 0; }
.callout p + p { margin-top: 10px; }