/* ============================================================
   CMU Computer Vision Group — Redesigned Stylesheet
   ============================================================ */

/* ---------- CSS Custom Properties ---------- */
:root {
  --color-cmu-red: #c41230;
  --color-cmu-dark: #1e1e1e;
  --color-bg: #ffffff;
  --color-bg-alt: #f5f5f5;
  --color-text: #222222;
  --color-text-muted: #555555;
  --color-border: #e0e0e0;
  --color-accent: var(--color-cmu-red);
  --color-link: var(--color-cmu-red);
  --color-link-hover: #a00e28;

  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);

  --max-width: 1200px;
  --nav-height: 64px;
}

/* ---------- Reset ---------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-weight: var(--font-weight-normal);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--color-link);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--color-link-hover);
}

ul, ol {
  list-style: none;
}

h1, h2, h3, h4 {
  line-height: 1.25;
  font-weight: var(--font-weight-bold);
}

h1 { font-size: 2.25rem; }
h2 { font-size: 1.75rem; }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.1rem; }

/* ---------- Layout Utilities ---------- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.section {
  padding: var(--space-3xl) 0;
}

.section--alt {
  background: var(--color-bg-alt);
}

.section__title {
  font-size: 1.75rem;
  margin-bottom: var(--space-xl);
  text-align: center;
}

/* ---------- Sticky Navigation ---------- */
.nav {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  height: var(--nav-height);
}

.nav__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav__logo img {
  height: 36px;
  width: auto;
}

.nav__links {
  display: flex;
  gap: var(--space-lg);
  align-items: center;
}

.nav__links a {
  color: var(--color-text);
  font-weight: var(--font-weight-medium);
  font-size: 0.95rem;
  padding: var(--space-xs) 0;
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-color 0.2s;
}

.nav__links a:hover,
.nav__links a.active {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

/* Hamburger (mobile) */
.nav__hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm);
}

.nav__hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  margin: 5px 0;
  transition: transform 0.3s, opacity 0.3s;
}

/* ---------- Hero Section ---------- */
.hero {
  position: relative;
  background: linear-gradient(rgba(0,0,0,0.55), rgba(0,0,0,0.55)),
              url('../assets/cmu.jpeg') center/cover no-repeat;
  color: #fff;
  padding: var(--space-3xl) 0;
  min-height: 380px;
  display: flex;
  align-items: center;
}

.hero__content {
  text-align: center;
  max-width: 700px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.hero__title {
  font-size: 2.75rem;
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--space-md);
  letter-spacing: -0.02em;
}

.hero__subtitle {
  font-size: 1.2rem;
  font-weight: var(--font-weight-normal);
  opacity: 0.9;
  line-height: 1.5;
}

/* ---------- Card Base ---------- */
.card {
  background: var(--color-bg);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: box-shadow 0.25s, transform 0.25s;
}

.card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

/* ---------- Card — Person ---------- */
.grid--people {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--space-xl);
}

.card--person {
  text-align: center;
  padding: var(--space-xl) var(--space-md) var(--space-lg);
}

.card--person__photo {
  width: 130px;
  height: 130px;
  border-radius: 50%;
  object-fit: cover;
  margin: 0 auto var(--space-md);
  border: 3px solid var(--color-border);
}

.card--person__name {
  font-size: 1.05rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-xs);
}

.card--person__name a {
  color: var(--color-text);
}

.card--person__name a:hover {
  color: var(--color-accent);
}

.card--person__interests {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.4;
}

/* ---------- Card — Project ---------- */
.grid--projects {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-xl);
}

.card--project__thumb {
  width: 100%;
  height: 180px;
  object-fit: cover;
}

.card--project__body {
  padding: var(--space-md);
}

.card--project__title {
  font-size: 0.95rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
  line-height: 1.35;
}

.card--project__title a {
  color: var(--color-text);
}

.card--project__title a:hover {
  color: var(--color-accent);
}

.card--project__meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

.card--project__year {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.card--project__tags {
  display: flex;
  gap: var(--space-xs);
  flex-wrap: wrap;
}

.tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: var(--font-weight-medium);
  padding: 2px 8px;
  border-radius: 999px;
  background: var(--color-bg-alt);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  white-space: nowrap;
}

/* ---------- Card — Course ---------- */
.grid--courses {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.card--course {
  display: flex;
  overflow: hidden;
}

.card--course__thumb {
  width: 280px;
  min-height: 180px;
  object-fit: cover;
  flex-shrink: 0;
}

.card--course__body {
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.card--course__number {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--space-xs);
}

.card--course__title {
  font-size: 1.15rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
}

.card--course__desc {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  line-height: 1.6;
  margin-bottom: var(--space-md);
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.card--course__link {
  font-size: 0.9rem;
  font-weight: var(--font-weight-medium);
}

/* ---------- Research Areas (Index) ---------- */
.grid--areas {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-lg);
}

.area-card {
  background: var(--color-bg);
  border-radius: var(--radius-md);
  padding: var(--space-xl) var(--space-lg);
  text-align: center;
  box-shadow: var(--shadow-sm);
  border-top: 3px solid var(--color-accent);
}

.area-card__icon {
  font-size: 2rem;
  margin-bottom: var(--space-md);
}

.area-card__title {
  font-size: 1.05rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
}

.area-card__desc {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.5;
}

/* ---------- Quick Links (Index) ---------- */
.quick-links {
  display: flex;
  justify-content: center;
  gap: var(--space-md);
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 0.7rem 1.5rem;
  border-radius: var(--radius-sm);
  font-weight: var(--font-weight-semibold);
  font-size: 0.95rem;
  cursor: pointer;
  transition: background 0.2s, color 0.2s;
  text-align: center;
  border: none;
}

.btn--primary {
  background: var(--color-accent);
  color: #fff;
}

.btn--primary:hover {
  background: var(--color-link-hover);
  color: #fff;
}

.btn--outline {
  background: transparent;
  color: var(--color-accent);
  border: 2px solid var(--color-accent);
}

.btn--outline:hover {
  background: var(--color-accent);
  color: #fff;
}

/* ---------- Filter Bar (Research) ---------- */
.filter-bar {
  display: flex;
  justify-content: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
  margin-bottom: var(--space-2xl);
}

.filter-btn {
  display: inline-block;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  color: var(--color-text-muted);
  font-size: 0.85rem;
  font-weight: var(--font-weight-medium);
  cursor: pointer;
  transition: all 0.2s;
  font-family: var(--font-body);
}

.filter-btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.filter-btn.active {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

/* ---------- Sponsorship Page ---------- */
.benefits-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-lg);
  margin-bottom: var(--space-3xl);
}

.benefit-card {
  background: var(--color-bg);
  border-radius: var(--radius-md);
  padding: var(--space-xl) var(--space-lg);
  box-shadow: var(--shadow-sm);
  text-align: center;
}

.benefit-card__icon {
  font-size: 2rem;
  margin-bottom: var(--space-md);
}

.benefit-card__title {
  font-size: 1.05rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
}

.benefit-card__desc {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.5;
}

/* Contact Form */
.contact-form {
  max-width: 600px;
  margin: 0 auto;
}

.contact-form .form-group {
  margin-bottom: var(--space-lg);
}

.contact-form label {
  display: block;
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--space-xs);
  font-size: 0.9rem;
}

.contact-form input,
.contact-form textarea {
  width: 100%;
  padding: 0.65rem 0.9rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-family: var(--font-body);
  font-size: 0.95rem;
  transition: border-color 0.2s;
}

.contact-form input:focus,
.contact-form textarea:focus {
  outline: none;
  border-color: var(--color-accent);
}

.contact-form textarea {
  min-height: 140px;
  resize: vertical;
}

.form-fallback {
  text-align: center;
  margin-top: var(--space-lg);
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

/* ---------- Page Header (non-hero) ---------- */
.page-header {
  background: var(--color-bg-alt);
  padding: var(--space-2xl) 0;
  text-align: center;
  border-bottom: 1px solid var(--color-border);
}

.page-header__title {
  font-size: 2rem;
  margin-bottom: var(--space-sm);
}

.page-header__subtitle {
  font-size: 1rem;
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto;
}

/* ---------- Footer ---------- */
.footer {
  background: var(--color-cmu-dark);
  color: #ccc;
  padding: var(--space-2xl) 0;
}

.footer__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--space-xl);
  flex-wrap: wrap;
}

.footer__brand img {
  height: 30px;
  margin-bottom: var(--space-md);
  filter: brightness(0) invert(1);
}

.footer__brand p {
  font-size: 0.85rem;
  line-height: 1.6;
}

.footer__links h4 {
  color: #fff;
  font-size: 0.9rem;
  margin-bottom: var(--space-sm);
}

.footer__links a {
  display: block;
  color: #aaa;
  font-size: 0.85rem;
  margin-bottom: var(--space-xs);
}

.footer__links a:hover {
  color: #fff;
}

.footer__bottom {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--space-lg) 0;
  border-top: 1px solid #333;
  margin-top: var(--space-xl);
  text-align: center;
  font-size: 0.8rem;
  color: #888;
}

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
  .grid--projects {
    grid-template-columns: repeat(2, 1fr);
  }

  .grid--areas {
    grid-template-columns: repeat(2, 1fr);
  }

  .benefits-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  :root {
    --nav-height: 56px;
  }

  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.4rem; }

  .hero__title { font-size: 2rem; }
  .hero__subtitle { font-size: 1rem; }
  .hero { min-height: 280px; padding: var(--space-2xl) 0; }

  /* Mobile nav */
  .nav__hamburger {
    display: block;
  }

  .nav__links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    flex-direction: column;
    padding: var(--space-md) var(--space-lg);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    gap: 0;
  }

  .nav__links.open {
    display: flex;
  }

  .nav__links a {
    padding: var(--space-sm) 0;
    border-bottom: none;
  }

  /* Grids */
  .grid--people {
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: var(--space-md);
  }

  .card--person {
    padding: var(--space-md) var(--space-sm) var(--space-md);
  }

  .card--person__photo {
    width: 100px;
    height: 100px;
  }

  .grid--projects {
    grid-template-columns: 1fr;
  }

  .grid--areas {
    grid-template-columns: 1fr;
  }

  .benefits-grid {
    grid-template-columns: 1fr;
  }

  /* Course card stacks on mobile */
  .card--course {
    flex-direction: column;
  }

  .card--course__thumb {
    width: 100%;
    height: 180px;
  }

  .footer__inner {
    flex-direction: column;
  }

  .quick-links {
    flex-direction: column;
    align-items: center;
  }
}

@media (max-width: 480px) {
  .grid--people {
    grid-template-columns: repeat(2, 1fr);
  }

  .filter-bar {
    gap: var(--space-xs);
  }

  .filter-btn {
    font-size: 0.78rem;
    padding: 0.35rem 0.75rem;
  }
}

/* ---------- Utility ---------- */
.text-center { text-align: center; }
.mt-0 { margin-top: 0; }
.mb-0 { margin-bottom: 0; }
.hidden { display: none !important; }