/* ============================================
   Ferhat Ozgur Catak — Personal Academic Site
   Design system: UiS-inspired + modern academic
   ============================================ */

/* ---------- CSS Variables ---------- */
:root {
  --uis-blue: #003B5C;
  --uis-accent: #F39C12;
  --uis-gray: #4D4D4D;
  --bg: #0B1220;
  --surface: #0F1A2B;
  --surface2: #FFFFFF;
  --muted-dark: rgba(255, 255, 255, 0.10);
  --muted-light: rgba(0, 0, 0, 0.08);
  --success: #22C55E;
  --danger: #EF4444;
  --text: #E2E8F0;
  --text-muted: rgba(226, 232, 240, 0.75);
  --heading: #F8FAFC;
  --radius: 0.6rem;
  --radius-2xl: 1rem;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.18);
  --transition: 0.2s ease;
}

.theme-light {
  --bg: #F8FAFC;
  --surface: #FFFFFF;
  --surface2: #0F1A2B;
  --text: #1E293B;
  --text-muted: rgba(30, 41, 59, 0.75);
  --heading: #0F172A;
  --muted-dark: rgba(0, 0, 0, 0.06);
  --muted-light: rgba(0, 0, 0, 0.08);
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
}

/* ---------- Reset & Base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; }
}

body {
  margin: 0;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 {
  font-family: 'Space Grotesk', sans-serif;
  color: var(--heading);
  margin-top: 0;
  line-height: 1.2;
}
h1 { font-size: clamp(2rem, 5vw, 3rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2rem); margin-bottom: 1rem; }
h3 { font-size: 1.25rem; }

a { color: var(--uis-accent); text-decoration: none; transition: color var(--transition); }
a:hover { color: #f5b041; }
a:focus-visible { outline: 2px solid var(--uis-accent); outline-offset: 2px; }

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

/* ---------- Layout ---------- */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section { padding: 2.5rem 0; }
.section--sm { padding: 2.5rem 0; }
.section--lg { padding: 5rem 0; }

/* ---------- Navbar ---------- */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--surface);
  border-bottom: 1px solid var(--muted-dark);
  padding: 0.75rem 0;
  backdrop-filter: blur(12px);
}
.navbar .container { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 1rem; }
.navbar__brand {
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--heading);
}
.navbar__brand:hover { color: var(--uis-accent); }
.navbar__nav { display: flex; align-items: center; gap: 0.5rem; flex-wrap: wrap; }
.navbar__link {
  padding: 0.5rem 0.75rem;
  color: var(--text-muted);
  font-size: 0.9375rem;
  border-radius: var(--radius);
}
.navbar__link:hover, .navbar__link[aria-current="page"] { color: var(--heading); background: var(--muted-dark); }
.navbar__cta {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  background: var(--uis-accent);
  color: #0B1220;
  font-weight: 600;
  border-radius: var(--radius);
  border: none;
  cursor: pointer;
  font-size: 0.9375rem;
}
.navbar__cta:hover { background: #f5b041; color: #0B1220; }
.navbar__cta:focus-visible { outline: 2px solid var(--uis-accent); outline-offset: 2px; }

/* Hamburger */
.navbar__toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  background: transparent;
  border: 1px solid var(--muted-dark);
  border-radius: var(--radius);
  color: var(--heading);
  cursor: pointer;
  aria-label: "Open menu";
}
.navbar__toggle:focus-visible { outline: 2px solid var(--uis-accent); outline-offset: 2px; }
.navbar__toggle[aria-expanded="true"] .navbar__icon--open { display: none; }
.navbar__toggle[aria-expanded="true"] .navbar__icon--close { display: block; }
.navbar__icon--close { display: none; }

@media (max-width: 768px) {
  .navbar__toggle { display: flex; }
  .navbar .container { flex-wrap: wrap; }
  .navbar__nav {
    display: none;
    width: 100%;
    flex-direction: column;
    align-items: stretch;
    padding-top: 1rem;
  }
  .navbar__nav.is-open { display: flex; }
  .navbar__link { padding: 0.75rem; }
}

/* Theme toggle */
.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.25rem;
  height: 2.25rem;
  padding: 0;
  background: var(--muted-dark);
  border: none;
  border-radius: var(--radius);
  color: var(--heading);
  cursor: pointer;
}
.theme-toggle:hover { background: var(--uis-accent); color: var(--bg); }
.theme-toggle:focus-visible { outline: 2px solid var(--uis-accent); outline-offset: 2px; }
.icon-moon { display: none; }
.theme-light .icon-sun { display: none; }
.theme-light .icon-moon { display: block; }

/* ---------- Hero ---------- */
.hero {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 2rem;
  align-items: center;
  padding: 1.75rem 0 1.75rem;
  max-width: 1040px;
  margin: 0 auto;
}
.hero__content { }
.hero__name { margin-bottom: 0.25rem; }
.hero__role { color: var(--text-muted); font-size: 1rem; margin-bottom: 1rem; }
.hero__headline { color: var(--heading); margin-bottom: 0.75rem; font-size: clamp(1.75rem, 4vw, 2.5rem); }
.hero__sub { color: var(--text-muted); font-size: 1.125rem; margin-bottom: 1.5rem; }
.hero__buttons { display: flex; flex-wrap: wrap; gap: 0.75rem; }
.hero__photo-wrap {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
}
.hero__photo-wrap::before {
  content: '';
  position: absolute;
  width: 320px;
  height: 320px;
  background: radial-gradient(circle at 30% 20%, rgba(243, 156, 18, 0.12), transparent 55%),
              radial-gradient(circle at 70% 80%, rgba(0, 59, 92, 0.35), transparent 60%);
  opacity: 0.8;
  border-radius: 40%;
  filter: blur(32px);
}
.hero__photo {
  position: relative;
  width: 280px;
  height: 280px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--muted-dark);
  background: var(--surface);
}

@media (max-width: 900px) {
  .hero { grid-template-columns: 1fr; text-align: center; min-height: auto; padding: 1.75rem 0 2rem; }
  .hero__buttons { justify-content: center; }
  .hero__photo-wrap { order: -1; }
}

/* ---------- Proof strip ---------- */
.proof-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  padding: 1.5rem 0;
  border-top: 1px solid var(--muted-dark);
  border-bottom: 1px solid var(--muted-dark);
}
.proof-strip__item {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 0.9rem;
  background: transparent;
  border-radius: 999px;
  border: 1px solid var(--muted-dark);
  font-size: 0.875rem;
  color: var(--text);
}
.proof-strip__item svg { flex-shrink: 0; color: var(--uis-accent); }

/* ---------- Cards ---------- */
.card {
  background: var(--surface);
  border-radius: var(--radius-2xl);
  padding: 1.5rem;
  border: 1px solid rgba(148, 163, 184, 0.35);
  box-shadow: var(--shadow);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.card:hover { transform: translateY(-1px); box-shadow: 0 4px 20px rgba(0, 0, 0, 0.25); border-color: rgba(148, 163, 184, 0.8); }
.theme-light .card:hover { box-shadow: 0 4px 20px rgba(15, 23, 42, 0.09); }
.card__image {
  width: 100%;
  height: 180px;
  object-fit: cover;
  border-radius: 0.6rem;
  margin-bottom: 0.75rem;
  border: 1px solid rgba(15, 23, 42, 0.5);
  background: #020617;
}
.card__title { margin-bottom: 0.5rem; }
.card__meta { color: var(--text-muted); font-size: 0.875rem; margin-bottom: 0.75rem; }
.card__text { color: var(--text-muted); font-size: 0.9375rem; margin-bottom: 1rem; }
.card__actions { display: flex; flex-wrap: wrap; gap: 0.5rem; }

.card--primary {
  border-color: var(--uis-accent);
  background: var(--surface);
  border-left-width: 3px;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  font-size: 0.9375rem;
  font-weight: 500;
  border-radius: var(--radius);
  border: none;
  cursor: pointer;
  transition: background var(--transition), color var(--transition);
  text-decoration: none;
}
.btn:focus-visible { outline: 2px solid var(--uis-accent); outline-offset: 2px; }
.btn--primary { background: var(--uis-accent); color: var(--bg); }
.btn--primary:hover { background: #f5b041; }
.btn--secondary { background: var(--muted-dark); color: var(--heading); }
.btn--secondary:hover { background: rgba(255,255,255,0.15); }
.btn--outline { background: transparent; border: 1px solid var(--muted-dark); color: var(--text); }
.btn--outline:hover { border-color: var(--uis-accent); color: var(--uis-accent); }

/* ---------- Grids ---------- */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.5rem; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.5rem; }
@media (max-width: 900px) {
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
}

/* ---------- Trustworthy AI Stack (signature diagram) ---------- */
.stack-diagram {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}
.stack-diagram--2col {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
  max-width: 640px;
}
@media (max-width: 560px) {
  .stack-diagram--2col { grid-template-columns: 1fr; }
}
.stack-layer {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.25rem;
  background: var(--surface);
  border-radius: var(--radius);
  border: 1px solid var(--muted-dark);
  border-left: 4px solid var(--uis-accent);
}
.stack-layer__icon { flex-shrink: 0; color: var(--uis-accent); }
.stack-layer__caption { font-size: 0.9375rem; color: var(--text); margin: 0; }

/* ---------- Publications list ---------- */
.pub-item {
  padding: 1rem 0;
  border-bottom: 1px solid var(--muted-dark);
}
.pub-item:last-child { border-bottom: none; }
.pub-item__title { font-weight: 600; margin-bottom: 0.25rem; }
.pub-item__venue { color: var(--text-muted); font-size: 0.875rem; margin-bottom: 0.25rem; }
.pub-item__contribution { font-size: 0.875rem; color: var(--text-muted); font-style: italic; margin-bottom: 0.5rem; }
.pub-item__links { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.pub-item__links .btn { padding: 0.25rem 0.5rem; font-size: 0.8125rem; }

/* ---------- Talks list ---------- */
.talk-item {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 1rem 0;
  border-bottom: 1px solid var(--muted-dark);
}
.talk-item:last-child { border-bottom: none; }
.talk-item__icon { flex-shrink: 0; color: var(--uis-accent); margin-top: 0.2rem; }
.talk-item__title { font-weight: 600; margin-bottom: 0.25rem; }
.talk-item__meta { color: var(--text-muted); font-size: 0.875rem; }

/* ---------- Timeline (activity) ---------- */
.timeline { position: relative; padding-left: 1.5rem; border-left: 2px solid var(--muted-dark); margin-left: 0.5rem; }
.timeline__item { position: relative; padding-bottom: 1.25rem; }
.timeline__item::before {
  content: '';
  position: absolute;
  left: -1.625rem;
  top: 0.4rem;
  width: 10px;
  height: 10px;
  background: var(--uis-accent);
  border-radius: 50%;
}
.timeline__date { font-size: 0.8125rem; color: var(--text-muted); margin-bottom: 0.25rem; }
.timeline__title { font-weight: 600; margin-bottom: 0.25rem; }
.timeline__desc { font-size: 0.875rem; color: var(--text-muted); }

/* ---------- FAQ ---------- */
.faq-list { }
.faq-item { padding: 1rem 0; border-bottom: 1px solid var(--muted-dark); }
.faq-item:last-child { border-bottom: none; }
.faq-item__q { font-weight: 600; margin-bottom: 0.5rem; color: var(--heading); }
.faq-item__a { color: var(--text-muted); font-size: 0.9375rem; margin: 0; }

/* ---------- Course cards ---------- */
.course-card {
  background: var(--surface);
  border-radius: var(--radius-2xl);
  padding: 1.5rem;
  border: 1px solid var(--muted-dark);
}
.course-card__code { font-size: 0.8125rem; color: var(--uis-accent); font-weight: 600; margin-bottom: 0.25rem; }
.course-card__name { font-weight: 600; margin-bottom: 0.75rem; }
.course-card__outcomes { margin: 0; padding-left: 1.25rem; font-size: 0.9375rem; color: var(--text-muted); }
.course-card__outcomes li { margin-bottom: 0.25rem; }

/* ---------- Footer ---------- */
.footer {
  background: var(--surface);
  border-top: 1px solid var(--muted-dark);
  padding: 3rem 0 2rem;
  margin-top: 4rem;
}
.footer .container { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 2rem; align-items: flex-start; }
.footer__brand { font-family: 'Space Grotesk', sans-serif; font-weight: 700; margin-bottom: 0.5rem; }
.footer__email { margin-bottom: 1rem; }
.footer__social { display: flex; gap: 0.75rem; flex-wrap: wrap; }
.footer__social a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  background: var(--muted-dark);
  border-radius: var(--radius);
  color: var(--text);
  transition: background var(--transition), color var(--transition);
}
.footer__social a:hover { background: var(--uis-accent); color: var(--bg); }
.footer__social a:focus-visible { outline: 2px solid var(--uis-accent); outline-offset: 2px; }
.footer__copy { width: 100%; margin-top: 2rem; padding-top: 1.5rem; border-top: 1px solid var(--muted-dark); font-size: 0.875rem; color: var(--text-muted); }
.footer__copy .keywords { opacity: 0.85; }

/* ---------- Page header ---------- */
.page-header { padding: 2rem 0; }
.page-header h1 { margin-bottom: 0.5rem; }
.page-header__sub { color: var(--text-muted); font-size: 1.125rem; }

/* ---------- Filters (projects) ---------- */
.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
  align-items: center;
}
.filters__search { flex: 1; min-width: 200px; }
.filters__search input {
  width: 100%;
  padding: 0.5rem 1rem;
  border: 1px solid var(--muted-dark);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font-size: 1rem;
}
.filters__search input:focus { outline: 2px solid var(--uis-accent); outline-offset: 0; }
.filter-tags { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.filter-tag {
  padding: 0.35rem 0.75rem;
  background: var(--muted-dark);
  border: none;
  border-radius: var(--radius);
  color: var(--text);
  font-size: 0.875rem;
  cursor: pointer;
}
.filter-tag:hover, .filter-tag.is-active { background: var(--uis-accent); color: var(--bg); }

/* ---------- Contact ---------- */
.contact-card {
  background: var(--surface);
  border-radius: var(--radius-2xl);
  padding: 2rem;
  border: 1px solid var(--muted-dark);
  max-width: 560px;
}
.contact-card__title { margin-bottom: 1rem; }
.checklist { list-style: none; padding: 0; margin: 0 0 1.5rem 0; }
.checklist li { padding: 0.5rem 0; padding-left: 1.5rem; position: relative; }
.checklist li::before { content: '✓'; position: absolute; left: 0; color: var(--success); font-weight: bold; }
.form-group { margin-bottom: 1rem; }
.form-group label { display: block; margin-bottom: 0.35rem; font-size: 0.875rem; }
.form-group input, .form-group textarea {
  width: 100%;
  padding: 0.6rem 0.75rem;
  border: 1px solid var(--muted-dark);
  border-radius: var(--radius);
  background: var(--bg);
  color: var(--text);
  font-family: inherit;
  font-size: 1rem;
}
.form-group textarea { min-height: 120px; resize: vertical; }
.form-group input:focus, .form-group textarea:focus { outline: 2px solid var(--uis-accent); outline-offset: 0; }

/* ---------- Breadcrumb ---------- */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}
.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--uis-accent); }
.breadcrumb span:last-child { color: var(--text); }

/* ---------- Utility ---------- */
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.text-center { text-align: center; }
.mb-0 { margin-bottom: 0; }
.mt-2 { margin-top: 2rem; }

/* ---------- Reveal (optional) ---------- */
.reveal { opacity: 0; transform: translateY(12px); transition: opacity 0.4s ease, transform 0.4s ease; }
.reveal.is-visible { opacity: 1; transform: translateY(0); }
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; }
  .reveal.is-visible { opacity: 1; transform: none; }
}