/* =============================================
   Academic Theme for Marcelo S. Guimarães
   UERJ — Departamento de Física Teórica
   ============================================= */

:root {
  --blue-900: #0F2D52;
  --blue-800: #163D6E;
  --blue-700: #1B4F8A;
  --blue-600: #2563A8;
  --blue-500: #3478BE;
  --blue-400: #5A9AD5;
  --blue-300: #8FBDE6;
  --blue-200: #B9D5F0;
  --blue-100: #D6E4F4;
  --blue-50:  #EDF3FA;

  --amber-600: #D97706;
  --amber-500: #E8913A;
  --amber-100: #FEF3C7;

  --gray-900: #1A1A2E;
  --gray-800: #2D2D44;
  --gray-700: #4A4A5A;
  --gray-600: #6B6B7B;
  --gray-500: #8E8E9A;
  --gray-400: #ACACB8;
  --gray-300: #CDCDD4;
  --gray-200: #E2E2E8;
  --gray-100: #F0F0F4;
  --gray-50:  #F8F8FB;

  --font-body: 'Source Sans 3', 'Segoe UI', system-ui, sans-serif;
  --font-heading: 'Playfair Display', Georgia, 'Times New Roman', serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

  --max-width: 1120px;
  --nav-height: 64px;
  --radius: 6px;
  --shadow-sm: 0 1px 3px rgba(15,45,82,0.08);
  --shadow-md: 0 4px 12px rgba(15,45,82,0.10);
  --shadow-lg: 0 8px 30px rgba(15,45,82,0.12);
  --transition: 0.25s ease;
}

/* --- RESET & BASE --- */

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

html {
  font-size: 17px;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + 1rem);
}

body {
  font-family: var(--font-body);
  color: var(--gray-800);
  background: var(--gray-50);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-family: var(--font-heading);
  color: var(--blue-900);
  line-height: 1.3;
}
h1 { font-size: 2.2rem; margin-bottom: 0.6em; }
h2 { font-size: 1.6rem; margin: 2rem 0 0.8rem; }
h3 { font-size: 1.25rem; margin: 1.5rem 0 0.6rem; }
h4 { font-size: 1.05rem; margin: 1.2rem 0 0.4rem; font-family: var(--font-body); font-weight: 700; }

p { margin-bottom: 1em; }

a {
  color: var(--blue-700);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { color: var(--amber-600); }

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

ul, ol { margin: 0.5em 0 1em 1.5em; }
li { margin-bottom: 0.3em; }

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--blue-50);
  padding: 0.15em 0.4em;
  border-radius: 3px;
}

pre {
  background: var(--gray-900);
  color: #e0e0e0;
  padding: 1.2em;
  border-radius: var(--radius);
  overflow-x: auto;
  margin: 1em 0;
}
pre code {
  background: transparent;
  padding: 0;
  color: inherit;
}

hr {
  border: none;
  border-top: 1px solid var(--gray-200);
  margin: 2rem 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 1.5rem;
  font-size: 0.95rem;
}
th, td {
  padding: 0.6em 0.8em;
  text-align: left;
  border-bottom: 1px solid var(--gray-200);
}
th {
  background: var(--blue-50);
  color: var(--blue-900);
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
tbody tr:hover { background: var(--gray-50); }

/* --- NAVIGATION --- */

.site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--blue-900);
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
  height: var(--nav-height);
}
.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}
.nav-brand {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  color: #fff;
  font-weight: 700;
  letter-spacing: 0.01em;
  white-space: nowrap;
}
.nav-brand:hover { color: var(--blue-200); }

.nav-links {
  display: flex;
  gap: 0.2rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-links a {
  display: block;
  color: var(--blue-200);
  padding: 0.4rem 0.7rem;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition);
}
.nav-links a:hover,
.nav-links a.active {
  color: #fff;
  background: rgba(255,255,255,0.12);
}

/* Language switcher */
.lang-switch {
  margin-left: 0.5rem;
  padding-left: 0.8rem;
  border-left: 1px solid rgba(255,255,255,0.2);
}
.lang-btn {
  display: inline-block;
  color: var(--blue-300) !important;
  padding: 0.3rem 0.6rem !important;
  border: 1px solid rgba(255,255,255,0.2);
  border-radius: var(--radius);
  font-size: 0.8rem !important;
  font-weight: 600 !important;
  letter-spacing: 0.02em;
  transition: all var(--transition);
}
.lang-btn:hover {
  color: #fff !important;
  background: rgba(255,255,255,0.15);
  border-color: rgba(255,255,255,0.4);
}

/* Hamburger menu for mobile */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
}
.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: #fff;
  margin: 5px 0;
  transition: var(--transition);
}

/* --- HERO / HOME --- */

.hero {
  background: linear-gradient(135deg, var(--blue-900) 0%, var(--blue-700) 100%);
  color: #fff;
  padding: 3rem 1.5rem 2.5rem;
}
.hero-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  gap: 2.5rem;
  align-items: center;
}
.hero-photo {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid rgba(255,255,255,0.3);
  flex-shrink: 0;
}
.hero-text h1 {
  color: #fff;
  font-size: 2.4rem;
  margin-bottom: 0.15em;
}
.hero-subtitle {
  font-size: 1.1rem;
  color: var(--blue-200);
  margin-bottom: 0.3rem;
}
.hero-tagline {
  font-size: 0.95rem;
  color: var(--blue-300);
  margin-bottom: 1.2rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  font-weight: 500;
}
.hero-links {
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
}
.hero-links a {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  color: #fff;
  background: rgba(255,255,255,0.12);
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius);
  font-size: 0.85rem;
  font-weight: 500;
  transition: all var(--transition);
}
.hero-links a:hover {
  background: rgba(255,255,255,0.22);
  color: #fff;
}
.hero-links svg {
  width: 16px;
  height: 16px;
}

/* --- PAGE LAYOUT --- */

.page-wrap {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1.5rem 3rem;
}

.page-header {
  border-bottom: 3px solid var(--blue-700);
  padding-bottom: 0.6rem;
  margin-bottom: 1.8rem;
}
.page-header h1 {
  font-size: 2rem;
}

/* Breadcrumbs */
.breadcrumb {
  font-size: 0.85rem;
  color: var(--gray-500);
  margin-bottom: 1rem;
}
.breadcrumb a { color: var(--blue-600); }
.breadcrumb span { margin: 0 0.3em; }

/* --- QUICK CARDS (Home page) --- */

.cards-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.2rem;
  margin: 2rem 0;
}
.card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: all var(--transition);
  text-align: center;
}
.card:hover {
  border-color: var(--blue-400);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}
.card-icon {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}
.card h3 {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 700;
  margin: 0;
  color: var(--blue-800);
}
.card p {
  font-size: 0.85rem;
  color: var(--gray-600);
  margin: 0.3em 0 0;
}

/* --- BIO SECTION --- */

.bio-section {
  background: #fff;
  border-radius: var(--radius);
  padding: 2rem;
  margin: 2rem 0;
  border: 1px solid var(--gray-200);
}
.bio-section h2 {
  font-size: 1.4rem;
  border-bottom: 2px solid var(--blue-100);
  padding-bottom: 0.4rem;
  margin-top: 0;
}

/* --- ANNOUNCEMENTS --- */

.announcements {
  margin: 2rem 0;
}
.announcement-item {
  background: #fff;
  border-left: 4px solid var(--amber-500);
  padding: 1rem 1.2rem;
  margin-bottom: 0.8rem;
  border-radius: 0 var(--radius) var(--radius) 0;
  box-shadow: var(--shadow-sm);
}
.announcement-item .date {
  font-size: 0.8rem;
  color: var(--gray-500);
  font-weight: 600;
  text-transform: uppercase;
}
.announcement-item h4 {
  margin: 0.2rem 0;
  font-size: 1rem;
}
.announcement-item p {
  font-size: 0.92rem;
  margin: 0.3em 0 0;
  color: var(--gray-700);
}

/* --- COURSE GRID --- */

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}
.course-card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 1.2rem 1.4rem;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
}
.course-card:hover {
  border-color: var(--blue-400);
  box-shadow: var(--shadow-md);
}
.course-card h3 {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 0.3rem;
  color: var(--blue-800);
}
.course-level {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.15em 0.5em;
  border-radius: 3px;
  margin-bottom: 0.5rem;
}
.course-level.grad {
  background: var(--blue-100);
  color: var(--blue-800);
}
.course-level.undergrad {
  background: var(--amber-100);
  color: var(--amber-600);
}

/* --- COURSE PAGE --- */

.course-meta {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 0.8rem;
  margin: 1rem 0 1.5rem;
  padding: 1rem;
  background: var(--blue-50);
  border-radius: var(--radius);
}
.course-meta-item {
  font-size: 0.9rem;
}
.course-meta-item strong {
  display: block;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--blue-700);
}

/* --- RESEARCH THEMES --- */

.research-theme {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 1.5rem 1.8rem;
  margin-bottom: 1.2rem;
  border-left: 4px solid var(--blue-700);
}
.research-theme h3 {
  color: var(--blue-800);
  margin-top: 0;
}

/* --- STUDENT SECTIONS --- */

.student-group {
  margin-bottom: 2rem;
}
.student-entry {
  padding: 0.6rem 0;
  border-bottom: 1px solid var(--gray-100);
}
.student-entry:last-child { border-bottom: none; }
.student-entry strong { color: var(--gray-900); }
.student-entry em { color: var(--gray-600); font-size: 0.92rem; }

/* --- COLLABORATORS --- */

.collab-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 0.8rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.collab-list li {
  background: var(--blue-50);
  padding: 0.7rem 1rem;
  border-radius: var(--radius);
}

/* --- FOOTER --- */

.site-footer {
  background: var(--blue-900);
  color: var(--blue-300);
  padding: 2rem 1.5rem;
  font-size: 0.85rem;
  margin-top: 3rem;
}
.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
.footer-inner a {
  color: var(--blue-200);
}
.footer-inner a:hover { color: #fff; }

/* --- BACK TO TOP --- */

.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  background: var(--blue-700);
  color: #fff;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  text-decoration: none;
  opacity: 0;
  pointer-events: none;
  transition: all var(--transition);
  box-shadow: var(--shadow-md);
}
.back-to-top.visible {
  opacity: 1;
  pointer-events: auto;
}
.back-to-top:hover {
  background: var(--amber-600);
  color: #fff;
}

/* --- MATH (KaTeX) --- */

.katex-display {
  margin: 1.2em 0;
  overflow-x: auto;
}

/* --- UTILITY --- */

.text-muted { color: var(--gray-500); }
.text-sm { font-size: 0.88rem; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mb-2 { margin-bottom: 1rem; }
.tag {
  display: inline-block;
  background: var(--blue-50);
  color: var(--blue-700);
  padding: 0.1em 0.5em;
  border-radius: 3px;
  font-size: 0.8rem;
  font-weight: 600;
}

/* --- FILE DOWNLOAD LINKS --- */

a[href$=".pdf"]::before {
  content: "📄 ";
}

/* --- RESPONSIVE --- */

@media (max-width: 768px) {
  html { font-size: 16px; }

  .nav-toggle { display: block; }
  .nav-links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--blue-900);
    flex-direction: column;
    padding: 0.5rem 1rem 1rem;
    box-shadow: 0 4px 12px rgba(0,0,0,0.2);
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 0.6rem 0.8rem; }

  .hero-inner {
    flex-direction: column;
    text-align: center;
  }
  .hero-photo { width: 140px; height: 140px; }
  .hero-links { justify-content: center; }
  .hero-text h1 { font-size: 1.8rem; }

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

  .footer-inner { flex-direction: column; text-align: center; }
}

@media (max-width: 480px) {
  .cards-row { grid-template-columns: 1fr; }
  .hero-links { flex-direction: column; align-items: center; }
}