/* Modern, frame-free layout for Math 213 — Victor Matveev */
:root {
  --njit-red: #8f1d2c;
  --nav-dark: #30343b;
  --ink: #24272b;
  --muted: #66707a;
  --page: #f4f6f8;
  --card: #ffffff;
  --line: #dfe3e7;
  --accent: #eaf4f8;
  --chapter: #fff2f2;
  --link: #7b1826;
  --max: 1180px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  color: var(--ink);
  background: var(--page);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.55;
}

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

.site-header {
  background: var(--njit-red);
  color: #fff;
  box-shadow: 0 2px 10px rgba(0,0,0,.12);
}

.header-inner {
  max-width: var(--max);
  margin: auto;
  padding: 24px 28px 18px;
  display: flex;
  justify-content: space-between;
  gap: 24px;
  align-items: center;
}

.eyebrow {
  font-size: .78rem;
  letter-spacing: .08em;
  text-transform: uppercase;
  opacity: .82;
}

h1 {
  margin: 2px 0 0;
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  line-height: 1.15;
}
.header-inner p { margin: 5px 0 0; opacity: .88; }

.top-nav {
  max-width: var(--max);
  margin: auto;
  padding: 0 28px 14px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.top-nav a {
  color: #fff;
  background: rgba(0,0,0,.20);
  padding: 7px 12px;
  border-radius: 6px;
  font-size: .9rem;
}
.top-nav a:hover { background: rgba(255,255,255,.14); text-decoration: none; }

.menu-toggle {
  display: none;
  border: 1px solid rgba(255,255,255,.45);
  background: transparent;
  color: white;
  padding: 8px 12px;
  border-radius: 6px;
  font: inherit;
}

.page-shell {
  max-width: var(--max);
  margin: 0 auto;
  padding: 28px;
  display: grid;
  grid-template-columns: 215px minmax(0, 1fr);
  gap: 28px;
  align-items: start;
}

.sidebar {
  position: sticky;
  top: 18px;
}

.profile-card {
  background: white;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px;
  margin-bottom: 16px;
}
.profile-card img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 6px;
}

.nav-group {
  background: white;
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow: hidden;
  margin-bottom: 14px;
}
.nav-group h2 {
  margin: 0;
  padding: 9px 12px;
  color: white;
  background: var(--nav-dark);
  font-size: .9rem;
}
.nav-group a {
  display: block;
  padding: 8px 12px;
  border-top: 1px solid #edf0f2;
  color: var(--ink);
  font-size: .9rem;
}
.nav-group a:hover {
  background: #fff8d9;
  text-decoration: none;
}
.nav-group a.featured { background: #fff8d9; }

.content { min-width: 0; }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 24px 28px;
  margin-bottom: 22px;
  box-shadow: 0 1px 3px rgba(0,0,0,.035);
}

.card h2 {
  margin: 0 0 16px;
  color: var(--njit-red);
  font-size: 1.25rem;
}
.card h3 {
  margin: 26px 0 8px;
  padding: 8px 12px;
  background: var(--chapter);
  border-left: 4px solid var(--njit-red);
  font-size: 1rem;
}
.card h3:first-of-type { margin-top: 4px; }

.intro {
  border-top: 5px solid var(--njit-red);
}
.intro h2 { margin-bottom: 3px; font-size: 1.5rem; }
.subtitle { color: var(--muted); margin: 0 0 16px; }

.button {
  display: inline-block;
  background: var(--njit-red);
  color: white;
  padding: 8px 13px;
  border-radius: 6px;
  font-size: .92rem;
}
.button:hover { background: #721522; text-decoration: none; }

.exam-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0,1fr));
  border: 1px solid var(--line);
  border-radius: 7px;
  overflow: hidden;
}
.exam-grid div {
  padding: 12px 14px;
  background: var(--accent);
  border: 1px solid white;
}
.exam-grid span {
  display: block;
  color: var(--muted);
  font-size: .88rem;
}
.exam-grid strong { display: block; margin-top: 2px; }

.resource-list {
  border: 1px solid var(--line);
  border-radius: 7px;
  overflow: hidden;
}
.resource-list > div {
  display: grid;
  grid-template-columns: 150px 1fr 1fr;
  gap: 12px;
  align-items: center;
  padding: 9px 12px;
  border-bottom: 1px solid var(--line);
}
.resource-list > div:last-child { border-bottom: 0; }
.resource-list.single > div { grid-template-columns: 150px 1fr; }
.resource-list span { color: #4f5962; }

footer {
  color: var(--muted);
  font-size: .88rem;
  padding: 0 4px 30px;
}

@media (max-width: 800px) {
  .header-inner { padding: 18px 18px 14px; }
  .menu-toggle { display: block; }
  .top-nav {
    display: none;
    padding: 0 18px 16px;
  }
  .top-nav.open { display: flex; }

  .page-shell {
    grid-template-columns: 1fr;
    padding: 18px;
  }

  .sidebar {
    position: static;
    order: 2;
  }
  .content { order: 1; }

  .profile-card { max-width: 190px; }

  .exam-grid { grid-template-columns: 1fr; }
  .resource-list > div,
  .resource-list.single > div {
    grid-template-columns: 1fr;
    gap: 2px;
  }
}

@media (max-width: 480px) {
  .card { padding: 18px; }
  h1 { font-size: 1.45rem; }
}