/* ================================================================
   DESIGN TOKENS
   Academic tone: cool slate surfaces, deep teal accent.
   Instrument Serif for display, Satoshi for body.
   ================================================================ */

:root {
  /* Typography */
  --font-display: 'Instrument Serif', Georgia, serif;
  --font-body: 'Satoshi', 'Inter', 'Helvetica Neue', sans-serif;

  /* Fluid Type Scale */
  --text-xs:   clamp(0.75rem,  0.7rem  + 0.25vw, 0.875rem);
  --text-sm:   clamp(0.875rem, 0.8rem  + 0.35vw, 1rem);
  --text-base: clamp(1rem,     0.95rem + 0.25vw, 1.125rem);
  --text-lg:   clamp(1.125rem, 1rem    + 0.75vw, 1.5rem);
  --text-xl:   clamp(1.5rem,   1.2rem  + 1.25vw, 2.25rem);
  --text-2xl:  clamp(2rem,     1.2rem  + 2.5vw,  3.5rem);
  --text-hero: clamp(3rem,     0.5rem  + 7vw,    5.5rem);

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

  /* Content Widths */
  --content-narrow: 640px;
  --content-default: 920px;
  --content-wide: 1100px;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Transitions */
  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

/* ================================================================
   LIGHT THEME (default)
   Cool academic palette: near-white background, slate text, teal accent.
   ================================================================ */
:root, [data-theme="light"] {
  --color-bg:             #f8f9fa;
  --color-surface:        #ffffff;
  --color-surface-2:      #f1f3f5;
  --color-surface-offset: #e9ecef;
  --color-divider:        #dee2e6;
  --color-border:         #ced4da;

  --color-text:           #1a1a2e;
  --color-text-muted:     #5c6370;
  --color-text-faint:     #adb5bd;
  --color-text-inverse:   #f8f9fa;

  --color-primary:        #0d6e6e;
  --color-primary-hover:  #0a5555;
  --color-primary-active: #084444;
  --color-primary-light:  #e6f2f2;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.07);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.1);
}

/* ================================================================
   DARK THEME
   ================================================================ */
[data-theme="dark"] {
  --color-bg:             #0f1117;
  --color-surface:        #181a20;
  --color-surface-2:      #1e2028;
  --color-surface-offset: #252730;
  --color-divider:        #2a2d38;
  --color-border:         #363944;

  --color-text:           #d1d5db;
  --color-text-muted:     #8b8f9a;
  --color-text-faint:     #555962;
  --color-text-inverse:   #0f1117;

  --color-primary:        #3fb8b8;
  --color-primary-hover:  #2d9e9e;
  --color-primary-active: #1f8484;
  --color-primary-light:  rgba(63, 184, 184, 0.1);

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5);
}

/* System preference fallback */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg:             #0f1117;
    --color-surface:        #181a20;
    --color-surface-2:      #1e2028;
    --color-surface-offset: #252730;
    --color-divider:        #2a2d38;
    --color-border:         #363944;
    --color-text:           #d1d5db;
    --color-text-muted:     #8b8f9a;
    --color-text-faint:     #555962;
    --color-text-inverse:   #0f1117;
    --color-primary:        #3fb8b8;
    --color-primary-hover:  #2d9e9e;
    --color-primary-active: #1f8484;
    --color-primary-light:  rgba(63, 184, 184, 0.1);
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5);
  }
}

/* ================================================================
   GLOBAL LAYOUT
   ================================================================ */
.container {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding-inline: var(--space-6);
}
.container--narrow {
  max-width: var(--content-narrow);
}

/* ================================================================
   HEADER
   Sticky, glass-effect, scroll-aware.
   ================================================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: oklch(from var(--color-bg) l c h / 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--color-divider);
  transition: transform 0.3s var(--ease-out), box-shadow 0.3s var(--ease-out);
}
.site-header--hidden {
  transform: translateY(-100%);
}
.site-header--scrolled {
  box-shadow: var(--shadow-sm);
}

.header-inner {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: var(--space-3) var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.header-logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  text-decoration: none;
  color: var(--color-text);
}
.logo-mark {
  flex-shrink: 0;
}
.header-name {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  letter-spacing: -0.01em;
}

/* Desktop nav */
.nav-desktop ul {
  display: flex;
  gap: var(--space-6);
}
.nav-desktop a {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  text-decoration: none;
  letter-spacing: 0.02em;
  position: relative;
}
.nav-desktop a::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 1.5px;
  background: var(--color-primary);
  transition: width 0.25s var(--ease-out);
}
.nav-desktop a:hover {
  color: var(--color-text);
}
.nav-desktop a:hover::after {
  width: 100%;
}

/* Header actions */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* Theme toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  color: var(--color-text-muted);
  transition: background var(--transition-interactive), color var(--transition-interactive);
}
.theme-toggle:hover {
  background: var(--color-surface-2);
  color: var(--color-text);
}
/* Show sun in dark mode, moon in light mode */
[data-theme="light"] .icon-sun,
:root:not([data-theme]) .icon-sun { display: none; }
[data-theme="light"] .icon-moon,
:root:not([data-theme]) .icon-moon { display: block; }
[data-theme="dark"] .icon-moon { display: none; }
[data-theme="dark"] .icon-sun { display: block; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) .icon-sun { display: block; }
  :root:not([data-theme]) .icon-moon { display: none; }
}

/* Hamburger */
.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 40px;
  height: 40px;
  padding: 8px;
  border-radius: var(--radius-md);
}
.hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
  transition: transform 0.3s var(--ease-out), opacity 0.3s var(--ease-out);
}
.hamburger[aria-expanded="true"] span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.hamburger[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}
.hamburger[aria-expanded="true"] span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Mobile nav */
.nav-mobile {
  padding: var(--space-4) var(--space-6) var(--space-8);
  border-top: 1px solid var(--color-divider);
}
.nav-mobile[hidden] { display: none; }
.nav-mobile ul {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}
.nav-mobile a {
  display: block;
  padding: var(--space-3) var(--space-4);
  font-size: var(--text-base);
  font-weight: 500;
  color: var(--color-text);
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: background var(--transition-interactive);
}
.nav-mobile a:hover,
.nav-mobile a:active {
  background: var(--color-surface-2);
}

@media (max-width: 767px) {
  .nav-desktop { display: none; }
  .hamburger { display: flex; }
}
@media (min-width: 768px) {
  .nav-mobile { display: none !important; }
}

/* ================================================================
   HERO SECTION
   ================================================================ */
.hero {
  position: relative;
  padding: clamp(var(--space-20), 12vw, var(--space-32)) var(--space-6);
  text-align: center;
  overflow: hidden;
}
.hero-label {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-primary);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: var(--space-4);
}
.hero-heading {
  font-family: var(--font-display);
  font-size: var(--text-hero);
  font-weight: 400;
  color: var(--color-text);
  letter-spacing: -0.02em;
  margin-bottom: var(--space-4);
  line-height: 1.05;
}
.hero-tagline {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  font-weight: 400;
  margin-bottom: var(--space-8);
  max-width: 42ch;
  margin-inline: auto;
}
.hero-cta {
  display: flex;
  justify-content: center;
  gap: var(--space-4);
  flex-wrap: wrap;
}

/* Decorative grid lines in hero */
.hero-decoration {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: -1;
}
.grid-line {
  position: absolute;
  background: var(--color-divider);
  opacity: 0.4;
}
.gl-1 {
  width: 1px;
  height: 100%;
  left: 20%;
}
.gl-2 {
  width: 1px;
  height: 100%;
  right: 20%;
}
.gl-3 {
  height: 1px;
  width: 100%;
  bottom: 0;
}

/* ================================================================
   BUTTONS
   ================================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-3) var(--space-6);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0.02em;
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: background var(--transition-interactive),
              color var(--transition-interactive),
              box-shadow var(--transition-interactive),
              transform var(--transition-interactive);
  cursor: pointer;
}
.btn:active {
  transform: translateY(1px);
}
.btn--primary {
  background: var(--color-primary);
  color: var(--color-text-inverse);
}
.btn--primary:hover {
  background: var(--color-primary-hover);
  box-shadow: var(--shadow-md);
}
.btn--outline {
  background: transparent;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}
.btn--outline:hover {
  background: var(--color-surface-2);
  border-color: var(--color-text-muted);
}
.btn--full {
  width: 100%;
}

/* ================================================================
   SECTIONS
   ================================================================ */
.section {
  padding: clamp(var(--space-12), 8vw, var(--space-24)) 0;
}
.section--alt {
  background: var(--color-surface);
}
.section-header {
  display: flex;
  align-items: baseline;
  gap: var(--space-4);
  margin-bottom: var(--space-10);
  padding-bottom: var(--space-3);
  border-bottom: 1px solid var(--color-divider);
}
.section-number {
  font-family: var(--font-body);
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: 0.05em;
}
.section-title {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 400;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

/* ================================================================
   ABOUT
   ================================================================ */
.about-content {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
}
@media (min-width: 768px) {
  .about-content {
    grid-template-columns: 2fr 1fr;
    gap: var(--space-12);
  }
}
.about-text p {
  font-size: var(--text-base);
  color: var(--color-text);
  line-height: 1.7;
  margin-bottom: var(--space-6);
}
.about-text p:last-child {
  margin-bottom: 0;
}
.about-details {
  padding: var(--space-6);
  background: var(--color-surface);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
}
[data-theme="dark"] .about-details,
.section--alt .about-details {
  background: var(--color-surface-2);
}
.about-details dl {
  display: grid;
  gap: var(--space-4);
}
.about-details dt {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.about-details dd {
  font-size: var(--text-sm);
  color: var(--color-text);
}

/* ================================================================
   RESEARCH INTERESTS — Card grid
   ================================================================ */
.research-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(280px, 100%), 1fr));
  gap: var(--space-6);
}
.research-card {
  padding: var(--space-6);
  background: var(--color-bg);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
  transition: box-shadow var(--transition-interactive), border-color var(--transition-interactive);
}
[data-theme="dark"] .research-card {
  background: var(--color-surface-2);
}
.research-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary);
}
.research-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: var(--color-primary-light);
  color: var(--color-primary);
  margin-bottom: var(--space-4);
}
.research-card h3 {
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}
.research-card p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* ================================================================
   DISSERTATION
   ================================================================ */
.dissertation-content {
  max-width: 65ch;
}
.dissertation-quote {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-style: italic;
  color: var(--color-text);
  padding-left: var(--space-6);
  border-left: 3px solid var(--color-primary);
  margin-bottom: var(--space-8);
  line-height: 1.5;
}
.dissertation-content p {
  font-size: var(--text-base);
  color: var(--color-text);
  line-height: 1.7;
  margin-bottom: var(--space-4);
}
.dissertation-content p:last-child {
  margin-bottom: 0;
}

/* ================================================================
   PUBLICATIONS
   ================================================================ */
.publications-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}
.pub-entry {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-6);
  padding: var(--space-6);
  background: var(--color-bg);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
}
[data-theme="dark"] .pub-entry {
  background: var(--color-surface-2);
}
.pub-year {
  font-family: var(--font-body);
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-primary);
  min-width: 3.5rem;
  padding-top: 2px;
}
.pub-title {
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}
.pub-meta {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
}
.pub-abstract {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
}
.pub-placeholder {
  font-size: var(--text-sm);
  color: var(--color-text-faint);
  font-style: italic;
}
.pub-entry--placeholder {
  border-style: dashed;
}

/* ================================================================
   PROJECTS
   ================================================================ */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(300px, 100%), 1fr));
  gap: var(--space-6);
}
.project-card {
  padding: var(--space-6);
  background: var(--color-surface);
  border: 1px solid var(--color-divider);
  border-radius: var(--radius-lg);
  transition: box-shadow var(--transition-interactive), border-color var(--transition-interactive);
}
[data-theme="dark"] .project-card {
  background: var(--color-surface-2);
}
.project-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary);
}
.project-tag {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-primary);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: var(--space-1) var(--space-3);
  background: var(--color-primary-light);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-3);
}
.project-title {
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}
.project-card > p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
  margin-bottom: var(--space-4);
}
.project-tech {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}
.project-tech li {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  padding: var(--space-1) var(--space-2);
  background: var(--color-surface-offset);
  border-radius: var(--radius-sm);
}

/* ================================================================
   CONTACT
   ================================================================ */
.contact-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
}
@media (min-width: 768px) {
  .contact-layout {
    grid-template-columns: 1.5fr 1fr;
    gap: var(--space-12);
  }
}
.contact-intro {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  margin-bottom: var(--space-6);
}
.contact-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}
.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.form-group label {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
}
.form-group input,
.form-group textarea {
  padding: var(--space-3) var(--space-4);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: var(--text-base);
  color: var(--color-text);
  transition: border-color var(--transition-interactive), box-shadow var(--transition-interactive);
}
[data-theme="dark"] .form-group input,
[data-theme="dark"] .form-group textarea {
  background: var(--color-surface-2);
}
.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
}
.form-group textarea {
  resize: vertical;
  min-height: 120px;
}
.form-status {
  font-size: var(--text-sm);
  color: var(--color-primary);
  min-height: 1.5em;
}

/* Contact sidebar links */
.contact-links h3 {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  color: var(--color-text);
  margin-bottom: var(--space-6);
}
.contact-links ul {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}
.contact-links a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  text-decoration: none;
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-divider);
  transition: background var(--transition-interactive),
              color var(--transition-interactive),
              border-color var(--transition-interactive);
}
.contact-links a:hover {
  background: var(--color-primary-light);
  color: var(--color-primary);
  border-color: var(--color-primary);
}
.contact-links a svg {
  flex-shrink: 0;
  display: inline;
}

/* ================================================================
   FOOTER
   ================================================================ */
.site-footer {
  padding: var(--space-8) 0;
  border-top: 1px solid var(--color-divider);
  text-align: center;
}
.site-footer p {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  max-width: none;
}
.footer-attribution {
  margin-top: var(--space-2);
}
.footer-attribution a {
  color: var(--color-text-faint);
  text-decoration: none;
}
.footer-attribution a:hover {
  color: var(--color-text-muted);
}

/* ================================================================
   SCROLL ANIMATIONS — JS IntersectionObserver driven (one-time reveal)
   Elements start hidden (via JS class), become visible permanently.
   ================================================================ */
.fade-in {
  opacity: 1; /* Fallback: always visible if JS fails */
}
.fade-in.fade-in--hidden {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out);
}
.fade-in.fade-in--visible {
  opacity: 1;
  transform: translateY(0);
}

/* ================================================================
   RESPONSIVE HELPERS
   ================================================================ */
.hide-mobile {
  display: none;
}
@media (min-width: 768px) {
  .hide-mobile { display: inline; }
}

/* Mobile refinements */
@media (max-width: 767px) {
  .hero {
    padding: var(--space-16) var(--space-4);
  }
  .pub-entry {
    grid-template-columns: 1fr;
    gap: var(--space-3);
  }
  .pub-year {
    min-width: unset;
  }
}