/* ═══════════════════════════════════════════════════════════
   Yağızhan Keskin — Personal Site
   Minimalist editorial portfolio
   ═══════════════════════════════════════════════════════════ */

/* ── Fonts ────────────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Inter:ital,opsz,wght@0,14..32,400;0,14..32,500;0,14..32,600;0,14..32,700;1,14..32,400&family=Source+Serif+4:ital,opsz,wght@0,8..60,500;1,8..60,500&display=swap');

/* ── Design Tokens ────────────────────────────────────────── */
:root {
  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  --font-serif: 'Source Serif 4', Georgia, 'Times New Roman', serif;

  /* Spacing scale (4px base) */
  --sp-1: 0.25rem;
  --sp-2: 0.5rem;
  --sp-3: 0.75rem;
  --sp-4: 1rem;
  --sp-5: 1.25rem;
  --sp-6: 1.5rem;
  --sp-8: 2rem;
  --sp-10: 2.5rem;
  --sp-12: 3rem;
  --sp-16: 4rem;
  --sp-20: 5rem;
  --sp-24: 6rem;
  --sp-32: 8rem;

  /* Layout */
  --max-width: 72rem;
  --content-width: 40rem;
  --wide-width: 56rem;

  /* Transitions */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --transition-fast: 150ms var(--ease-out);
  --transition-base: 300ms var(--ease-out);
  --transition-slow: 500ms var(--ease-out);

  /* Border radius */
  --radius-sm: 3px;
  --radius-md: 5px;
  --radius-lg: 8px;
}

/* ── Light Mode (default) ─────────────────────────────────── */
:root,
[data-theme="light"] {
  --color-bg: #fafaf9;
  --color-bg-elevated: #ffffff;
  --color-bg-subtle: #f5f5f4;
  --color-surface: #e7e5e4;

  --color-text-primary: #1c1917;
  --color-text-secondary: #57534e;
  --color-text-tertiary: #a8a29e;
  --color-text-inverse: #fafaf9;

  --color-border: #e7e5e4;
  --color-border-subtle: #f5f5f4;

  --color-accent: #3b6b96;
  --color-accent-hover: #2e5678;
  --color-accent-subtle: rgba(59, 107, 150, 0.06);

  --color-link: #3b6b96;
  --color-link-hover: #2e5678;

  --shadow-sm: 0 1px 2px rgba(28, 25, 23, 0.04);
  --shadow-md: 0 2px 8px rgba(28, 25, 23, 0.06);

  --nav-bg: rgba(250, 250, 249, 0.88);
  --nav-border: rgba(231, 229, 228, 0.6);
}

/* ── Dark Mode ────────────────────────────────────────────── */
[data-theme="dark"] {
  --color-bg: #111110;
  --color-bg-elevated: #1a1a19;
  --color-bg-subtle: #1e1e1d;
  --color-surface: #292928;

  --color-text-primary: #e7e5e4;
  --color-text-secondary: #a8a29e;
  --color-text-tertiary: #78716c;
  --color-text-inverse: #1c1917;

  --color-border: #292928;
  --color-border-subtle: #1e1e1d;

  --color-accent: #7aaccf;
  --color-accent-hover: #95bfdb;
  --color-accent-subtle: rgba(122, 172, 207, 0.07);

  --color-link: #7aaccf;
  --color-link-hover: #95bfdb;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.3);

  --nav-bg: rgba(17, 17, 16, 0.88);
  --nav-border: rgba(41, 41, 40, 0.6);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--color-text-primary);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition:
    background-color var(--transition-base),
    color var(--transition-base);
}

/* Prevent flash of wrong theme */
body.no-transition,
body.no-transition * {
  transition: none !important;
}

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

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

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

ul, ol {
  list-style: none;
}

button {
  border: none;
  background: none;
  cursor: pointer;
  font-family: inherit;
  color: inherit;
}

/* ── Focus States ─────────────────────────────────────────── */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ── Navigation ───────────────────────────────────────────── */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: var(--nav-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--nav-border);
  transition:
    background var(--transition-base),
    border-color var(--transition-base);
}

.nav__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--sp-6);
  height: 3.75rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav__name {
  font-weight: 700;
  font-size: 0.9375rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--color-text-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.nav__name:hover {
  color: var(--color-accent);
}

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--sp-1);
}

.nav__link {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  padding: var(--sp-2) var(--sp-3);
  border-radius: var(--radius-sm);
  transition:
    color var(--transition-fast),
    background-color var(--transition-fast);
  text-decoration: none;
}

.nav__link:hover {
  color: var(--color-text-primary);
  background-color: var(--color-accent-subtle);
}

.nav__link.active {
  color: var(--color-text-primary);
}

/* Theme toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
  transition:
    color var(--transition-fast),
    background-color var(--transition-fast);
  margin-left: var(--sp-2);
}

.theme-toggle:hover {
  color: var(--color-text-primary);
  background-color: var(--color-accent-subtle);
}

.theme-toggle svg {
  width: 1.125rem;
  height: 1.125rem;
}

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  display: none;
}

[data-theme="light"] .theme-toggle .icon-moon {
  display: block;
}

[data-theme="dark"] .theme-toggle .icon-sun {
  display: block;
}

/* Mobile menu */
.nav__mobile-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  color: var(--color-text-secondary);
}

.nav__mobile-toggle svg {
  width: 1.25rem;
  height: 1.25rem;
}

/* ── Layout ───────────────────────────────────────────────── */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--sp-6);
}

.section {
  padding: var(--sp-24) 0;
}

.section--compact {
  padding: var(--sp-16) 0;
}

.section__header {
  margin-bottom: var(--sp-12);
}

.section__label {
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-accent);
  margin-bottom: var(--sp-3);
}

.section__title {
  font-size: clamp(1.5rem, 3vw, 1.875rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  color: var(--color-text-primary);
}

.section__divider {
  width: 2rem;
  height: 1.5px;
  background: var(--color-accent);
  margin-top: var(--sp-4);
  border-radius: 1px;
  opacity: 0.7;
}

/* Text content constraint */
.text-content {
  max-width: var(--content-width);
}

.text-content--wide {
  max-width: var(--wide-width);
}

/* ── Hero ─────────────────────────────────────────────────── */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--sp-32);
  padding-bottom: var(--sp-16);
}

.hero__content {
  max-width: var(--wide-width);
}

.hero__eyebrow {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-accent);
  letter-spacing: 0.04em;
  margin-bottom: var(--sp-6);
  opacity: 0;
  transform: translateY(12px);
  animation: fadeInUp 0.6s var(--ease-out) 0.15s forwards;
}

.hero__name {
  font-size: clamp(2.5rem, 6vw, 4.25rem);
  font-weight: 700;
  letter-spacing: -0.035em;
  line-height: 1.05;
  color: var(--color-text-primary);
  margin-bottom: var(--sp-6);
  opacity: 0;
  transform: translateY(16px);
  animation: fadeInUp 0.6s var(--ease-out) 0.25s forwards;
}

.hero__positioning {
  font-family: var(--font-serif);
  font-size: clamp(1.125rem, 2.5vw, 1.375rem);
  font-weight: 500;
  font-style: italic;
  line-height: 1.55;
  color: var(--color-text-secondary);
  max-width: 36rem;
  margin-bottom: var(--sp-8);
  padding-left: var(--sp-6);
  border-left: 2px solid var(--color-accent);
  opacity: 0;
  transform: translateY(16px);
  animation: fadeInUp 0.6s var(--ease-out) 0.4s forwards;
}

.hero__description {
  font-size: 1rem;
  line-height: 1.75;
  color: var(--color-text-secondary);
  max-width: 32rem;
  margin-bottom: var(--sp-10);
  opacity: 0;
  transform: translateY(16px);
  animation: fadeInUp 0.6s var(--ease-out) 0.55s forwards;
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3);
  opacity: 0;
  transform: translateY(12px);
  animation: fadeInUp 0.6s var(--ease-out) 0.7s forwards;
}

/* ── Buttons ──────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  padding: 0.625rem 1.25rem;
  border-radius: var(--radius-md);
  transition:
    background-color var(--transition-fast),
    color var(--transition-fast),
    box-shadow var(--transition-fast),
    transform var(--transition-fast);
  text-decoration: none;
  cursor: pointer;
}

.btn:active {
  transform: scale(0.98);
}

.btn--primary {
  background-color: var(--color-accent);
  color: var(--color-text-inverse);
}

.btn--primary:hover {
  background-color: var(--color-accent-hover);
  color: var(--color-text-inverse);
  box-shadow: var(--shadow-md);
}

.btn--secondary {
  background-color: var(--color-accent-subtle);
  color: var(--color-accent);
  border: 1px solid transparent;
}

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

.btn svg {
  width: 1rem;
  height: 1rem;
  flex-shrink: 0;
}

/* ── About ────────────────────────────────────────────────── */
.about__text {
  max-width: var(--content-width);
}

.about__text p {
  font-size: 1.0625rem;
  line-height: 1.8;
  color: var(--color-text-secondary);
  margin-bottom: var(--sp-6);
}

.about__text p:last-child {
  margin-bottom: 0;
}

/* ── Experience / Timeline ────────────────────────────────── */
.experience-list {
  max-width: var(--wide-width);
  display: flex;
  flex-direction: column;
  gap: var(--sp-1);
}

.experience-item {
  display: grid;
  grid-template-columns: 10rem 1fr;
  gap: var(--sp-8);
  padding: var(--sp-6) 0;
  border-bottom: 1px solid var(--color-border);
}

.experience-item:last-child {
  border-bottom: none;
}

.experience__period {
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-tertiary);
  padding-top: var(--sp-1);
  letter-spacing: 0.01em;
}

.experience__details {
  max-width: var(--content-width);
}

.experience__role {
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--sp-1);
  letter-spacing: -0.01em;
}

.experience__org {
  font-size: 0.9375rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--sp-3);
}

.experience__description {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--color-text-secondary);
}

/* ── Academic ─────────────────────────────────────────────── */
.academic-block {
  max-width: var(--wide-width);
}

.academic__university {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--sp-2);
  letter-spacing: -0.015em;
}

.academic__location {
  font-size: 0.9375rem;
  color: var(--color-text-tertiary);
  margin-bottom: var(--sp-8);
}

.degree-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-6);
}

.degree-item {
  padding-left: var(--sp-6);
  border-left: 2px solid var(--color-border);
  transition: border-color var(--transition-fast);
}

.degree-item:hover {
  border-left-color: var(--color-accent);
}

.degree__type {
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-accent);
  margin-bottom: var(--sp-1);
}

.degree__name {
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--color-text-primary);
  letter-spacing: -0.01em;
}

.degree__note {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-top: var(--sp-1);
}

/* Certifications */
.certifications {
  margin-top: var(--sp-12);
  max-width: var(--wide-width);
}

.certifications__heading {
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-tertiary);
  margin-bottom: var(--sp-6);
  padding-bottom: var(--sp-3);
  border-bottom: 1px solid var(--color-border);
}

.cert-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(18rem, 1fr));
  gap: var(--sp-4);
}

.cert-item {
  display: flex;
  flex-direction: column;
  gap: var(--sp-1);
  padding: var(--sp-4) var(--sp-5);
  border-left: 2px solid var(--color-border);
  transition: border-color var(--transition-fast);
}

.cert-item:hover {
  border-left-color: var(--color-accent);
}

.cert__name {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-text-primary);
  letter-spacing: -0.01em;
  line-height: 1.35;
}

.cert__issuer {
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
}

.cert__badge {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-accent);
  padding: var(--sp-3) var(--sp-5);
  border: 1px solid var(--color-accent);
  border-radius: var(--radius-md);
  width: fit-content;
  letter-spacing: 0.02em;
}

.cert__badge-label {
  font-weight: 500;
  color: var(--color-text-secondary);
}

/* ── Focus Areas ──────────────────────────────────────────── */
.focus-grid {
  max-width: var(--wide-width);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr));
  gap: var(--sp-6);
}

.focus-item {
  padding: var(--sp-6);
  border: 1px solid var(--color-border);
  border-top: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  transition:
    border-color var(--transition-fast),
    background-color var(--transition-fast),
    box-shadow var(--transition-fast);
}

.focus-item:hover {
  border-color: var(--color-border);
  border-top-color: var(--color-accent);
  background-color: var(--color-accent-subtle);
  box-shadow: var(--shadow-md);
}

.focus__title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--sp-2);
  letter-spacing: -0.01em;
}

.focus__description {
  font-size: 0.875rem;
  line-height: 1.65;
  color: var(--color-text-secondary);
}

/* ── Leadership & Teaching ────────────────────────────────── */
.leadership-list {
  max-width: var(--wide-width);
  display: flex;
  flex-direction: column;
  gap: var(--sp-10);
}

.leadership-item {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--sp-3);
}

.leadership__role {
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--color-text-primary);
  letter-spacing: -0.01em;
}

.leadership__org {
  font-size: 0.9375rem;
  color: var(--color-accent);
}

.leadership__description {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--color-text-secondary);
  max-width: var(--content-width);
}

/* ── Working Style ────────────────────────────────────────── */
.style-grid {
  max-width: var(--wide-width);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
  gap: var(--sp-8);
}

.style-item {
  padding-left: var(--sp-5);
  border-left: 2px solid var(--color-border);
  transition: border-color var(--transition-fast);
}

.style-item:hover {
  border-left-color: var(--color-accent);
}

.style__title {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--sp-2);
}

.style__description {
  font-size: 0.875rem;
  line-height: 1.65;
  color: var(--color-text-secondary);
}

/* ── Contact ──────────────────────────────────────────────── */
.contact-section {
  border-top: 1px solid var(--color-border);
}

.contact__intro {
  font-size: 1.0625rem;
  line-height: 1.75;
  color: var(--color-text-secondary);
  max-width: var(--content-width);
  margin-bottom: var(--sp-8);
}

.contact__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3);
}

.contact__link {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  padding: var(--sp-3) var(--sp-5);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition:
    color var(--transition-fast),
    border-color var(--transition-fast),
    background-color var(--transition-fast);
  text-decoration: none;
}

.contact__link:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
  background-color: var(--color-accent-subtle);
}

.contact__link svg {
  width: 1rem;
  height: 1rem;
  flex-shrink: 0;
}

/* ── Footer ───────────────────────────────────────────────── */
.footer {
  padding: var(--sp-12) 0 var(--sp-10);
  border-top: 1px solid var(--color-border);
}

.footer__inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer__text {
  font-size: 0.75rem;
  color: var(--color-text-tertiary);
  letter-spacing: 0.02em;
}

.footer__link {
  font-size: 0.75rem;
  color: var(--color-text-tertiary);
  text-decoration: none;
  letter-spacing: 0.02em;
  transition: color var(--transition-fast);
}

.footer__link:hover {
  color: var(--color-accent);
}

/* ── Animations ───────────────────────────────────────────── */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Scroll reveal */
.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition:
    opacity 0.6s var(--ease-out),
    transform 0.6s var(--ease-out);
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ── Responsive ───────────────────────────────────────────── */

/* Tablet */
@media (max-width: 64rem) {
  .experience-item {
    grid-template-columns: 8rem 1fr;
    gap: var(--sp-5);
  }
}

/* Mobile */
@media (max-width: 48rem) {
  .section {
    padding: var(--sp-16) 0;
  }

  .section--compact {
    padding: var(--sp-12) 0;
  }

  .section__header {
    margin-bottom: var(--sp-8);
  }

  .hero {
    min-height: auto;
    padding-top: 7rem;
    padding-bottom: var(--sp-12);
  }

  .hero__name {
    font-size: clamp(2rem, 8vw, 2.75rem);
  }

  /* Nav mobile layout */
  .nav__links {
    position: fixed;
    top: 3.75rem;
    left: 0;
    right: 0;
    background: var(--nav-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--nav-border);
    flex-direction: column;
    padding: var(--sp-4) var(--sp-6);
    gap: 0;
    opacity: 0;
    pointer-events: none;
    transform: translateY(-8px);
    transition:
      opacity var(--transition-fast),
      transform var(--transition-fast);
  }

  .nav__links.open {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
  }

  .nav__link {
    width: 100%;
    padding: var(--sp-3) var(--sp-3);
    font-size: 0.875rem;
  }

  .theme-toggle {
    margin-left: 0;
    margin-top: var(--sp-2);
    align-self: flex-start;
  }

  .nav__mobile-toggle {
    display: flex;
  }

  /* Experience mobile */
  .experience-item {
    grid-template-columns: 1fr;
    gap: var(--sp-2);
  }

  .experience__period {
    padding-top: 0;
  }

  /* Focus grid mobile */
  .focus-grid {
    grid-template-columns: 1fr;
  }

  /* Style grid mobile */
  .style-grid {
    grid-template-columns: 1fr;
  }

  /* Footer mobile */
  .footer__inner {
    flex-direction: column;
    gap: var(--sp-3);
    text-align: center;
  }
}

/* Small mobile */
@media (max-width: 30rem) {
  .container {
    padding: 0 var(--sp-4);
  }

  .nav__inner {
    padding: 0 var(--sp-4);
  }

  .hero__actions {
    flex-direction: column;
    width: 100%;
  }

  .hero__actions .btn {
    justify-content: center;
  }

  .contact__links {
    flex-direction: column;
  }

  .contact__link {
    justify-content: center;
  }
}

/* ── Print styles ─────────────────────────────────────────── */
@media print {
  .nav,
  .theme-toggle,
  .nav__mobile-toggle {
    display: none;
  }

  .section {
    padding: var(--sp-8) 0;
  }

  body {
    font-size: 11pt;
    color: #000;
    background: #fff;
  }
}

/* ── Reduced motion ───────────────────────────────────────── */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }

  html {
    scroll-behavior: auto;
  }
}