/* ============================================
   Dr Parris Williams — Professional Website
   ============================================ */

/* --- Custom Properties --- */
:root {
  --color-primary: #0f1b2d;
  --color-primary-mid: #1a2d4a;
  --color-primary-light: #243b5e;
  --color-accent: #3d8b8b;
  --color-accent-light: #4ea9a9;
  --color-accent-glow: rgba(61, 139, 139, 0.15);
  --color-accent-hover: #2d6e6e;
  --color-gold: #c4a052;
  --color-gold-light: #d4b56a;
  --color-text: #2a2a2a;
  --color-text-light: #5c6370;
  --color-text-muted: #8b919a;
  --color-bg: #ffffff;
  --color-bg-warm: #fafaf8;
  --color-bg-alt: #f4f5f7;
  --color-bg-dark: #0f1b2d;
  --color-border: #e4e6ea;
  --color-border-light: #eef0f3;
  --color-white: #ffffff;

  --font-heading: 'Lora', Georgia, serif;
  --font-body: 'Source Sans 3', 'Source Sans Pro', -apple-system, BlinkMacSystemFont, sans-serif;

  --max-width: 900px;
  --max-width-wide: 1040px;
  --nav-height: 72px;

  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 3rem;
  --space-xl: 5rem;
  --space-2xl: 7rem;

  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;

  --shadow-sm: 0 1px 3px rgba(15, 27, 45, 0.04), 0 1px 2px rgba(15, 27, 45, 0.06);
  --shadow-md: 0 4px 16px rgba(15, 27, 45, 0.06), 0 2px 6px rgba(15, 27, 45, 0.04);
  --shadow-lg: 0 12px 40px rgba(15, 27, 45, 0.08), 0 4px 12px rgba(15, 27, 45, 0.04);
  --shadow-xl: 0 20px 60px rgba(15, 27, 45, 0.1), 0 8px 20px rgba(15, 27, 45, 0.06);
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
}

body {
  font-family: var(--font-body);
  font-size: 1.06rem;
  line-height: 1.75;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

a:hover,
a:focus {
  color: var(--color-accent-hover);
}

a:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
  border-radius: 2px;
}

h1, h2, h3 {
  font-family: var(--font-heading);
  color: var(--color-primary);
  line-height: 1.25;
  letter-spacing: -0.01em;
}

h1 {
  font-size: 3.2rem;
  font-weight: 700;
}

h2 {
  font-size: 2rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
}

h3 {
  font-size: 1.15rem;
  font-weight: 600;
}

/* --- Skip Link --- */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-sm);
  background: var(--color-primary);
  color: var(--color-white);
  padding: var(--space-xs) var(--space-sm);
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  z-index: 1000;
  font-size: 0.9rem;
}

.skip-link:focus {
  top: 0;
  color: var(--color-white);
}

/* ============================================
   Navigation
   ============================================ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-height);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-light);
  transition: box-shadow 0.3s ease;
}

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

.nav-logo {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-primary);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.nav-logo:hover,
.nav-logo:focus {
  color: var(--color-accent);
}

.nav-menu {
  list-style: none;
  display: flex;
  gap: 0.25rem;
}

.nav-menu a {
  display: block;
  color: var(--color-text-light);
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-sm);
  letter-spacing: 0.01em;
  text-transform: uppercase;
  transition: color 0.2s ease, background-color 0.2s ease;
}

.nav-menu a:hover,
.nav-menu a:focus {
  color: var(--color-accent);
  background-color: var(--color-accent-glow);
}

/* Hamburger */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-xs);
  flex-direction: column;
  gap: 5px;
}

.nav-toggle-bar {
  display: block;
  width: 22px;
  height: 2px;
  background-color: var(--color-primary);
  border-radius: 2px;
  transition: transform 0.3s ease, opacity 0.3s ease;
}

/* ============================================
   Hero
   ============================================ */
.hero {
  position: relative;
  padding: var(--space-2xl) var(--space-md);
  background: linear-gradient(135deg, #0f1b2d 0%, #1a3150 40%, #1e3a5f 70%, #1a2d4a 100%);
  overflow: hidden;
}

/* Subtle decorative pattern */
.hero::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background:
    radial-gradient(ellipse 80% 60% at 70% 40%, rgba(61, 139, 139, 0.12) 0%, transparent 70%),
    radial-gradient(ellipse 50% 80% at 20% 80%, rgba(196, 160, 82, 0.06) 0%, transparent 60%);
  pointer-events: none;
}

.hero-content {
  position: relative;
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

.hero-text {
  flex: 1;
}

.hero-text h1 {
  color: var(--color-white);
  margin-bottom: var(--space-sm);
}

.hero-tagline {
  font-size: 1.2rem;
  color: rgba(255, 255, 255, 0.7);
  margin-bottom: var(--space-lg);
  line-height: 1.7;
  max-width: 480px;
}

.hero-image {
  flex-shrink: 0;
}

.hero-image img {
  width: 260px;
  height: 260px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid rgba(255, 255, 255, 0.15);
  box-shadow:
    0 0 0 8px rgba(61, 139, 139, 0.12),
    0 20px 50px rgba(0, 0, 0, 0.3);
}

/* ============================================
   Buttons
   ============================================ */
.btn {
  display: inline-block;
  font-family: var(--font-body);
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.8rem 2rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  letter-spacing: 0.02em;
  transition: all 0.25s ease;
  cursor: pointer;
}

.btn-primary {
  background-color: var(--color-accent);
  color: var(--color-white);
  box-shadow: 0 2px 8px rgba(61, 139, 139, 0.3);
}

.btn-primary:hover,
.btn-primary:focus {
  background-color: var(--color-accent-light);
  color: var(--color-white);
  box-shadow: 0 4px 16px rgba(61, 139, 139, 0.35);
  transform: translateY(-1px);
}

/* Hero-specific button override */
.hero .btn-primary {
  background: var(--color-white);
  color: var(--color-primary);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.15);
}

.hero .btn-primary:hover,
.hero .btn-primary:focus {
  background: var(--color-white);
  color: var(--color-accent);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
  transform: translateY(-1px);
}

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

.btn-secondary:hover,
.btn-secondary:focus {
  background-color: var(--color-accent);
  color: var(--color-white);
  box-shadow: 0 2px 12px rgba(61, 139, 139, 0.25);
  transform: translateY(-1px);
}

/* ============================================
   Sections
   ============================================ */
.section {
  padding: var(--space-2xl) var(--space-md);
}

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

.section-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.section-inner p {
  margin-bottom: var(--space-sm);
  color: var(--color-text-light);
}

.section-label {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: var(--space-xs);
}

.section-intro {
  color: var(--color-text-light);
  margin-bottom: var(--space-lg);
  font-size: 1.08rem;
}

/* Decorative line under h2 */
.section-inner h2 {
  position: relative;
  padding-bottom: var(--space-md);
  margin-bottom: var(--space-md);
}

.section-inner h2::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 48px;
  height: 3px;
  background: linear-gradient(90deg, var(--color-accent), var(--color-accent-light));
  border-radius: 2px;
}

/* ============================================
   About
   ============================================ */
#about .section-inner p {
  font-size: 1.08rem;
  line-height: 1.8;
}

/* ============================================
   Publications / Research
   ============================================ */
.publications-grid {
  display: grid;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.publication-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-md) var(--space-md) var(--space-md) var(--space-md);
  position: relative;
  transition: box-shadow 0.25s ease, transform 0.25s ease;
  display: flex;
  gap: var(--space-md);
  align-items: flex-start;
}

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

.publication-year {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 56px;
  height: 32px;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--color-accent);
  background: var(--color-accent-glow);
  border-radius: var(--radius-sm);
  letter-spacing: 0.02em;
  flex-shrink: 0;
}

.publication-body {
  flex: 1;
  min-width: 0;
}

.publication-title {
  margin-bottom: 0.25rem;
  line-height: 1.45;
  color: var(--color-primary);
}

.publication-title a {
  color: inherit;
  text-decoration: none;
  transition: color 0.2s ease;
}

.publication-title a:hover {
  color: var(--color-accent);
}

.publication-journal {
  font-size: 0.92rem;
  color: var(--color-text-muted);
  font-style: italic;
}

.publication-doi {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin-top: 0.25rem;
  font-family: var(--font-body);
  opacity: 0.7;
  margin-bottom: 0;
}

.publications-cta {
  text-align: center;
}

/* ============================================
   Opportunities
   ============================================ */
.opportunities-list {
  list-style: none;
  margin: var(--space-md) 0 var(--space-lg);
  display: grid;
  gap: var(--space-sm);
}

.opportunities-list li {
  padding: var(--space-md);
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-accent);
  border-radius: var(--radius-sm);
  transition: box-shadow 0.2s ease, transform 0.2s ease;
}

.opportunities-list li:hover {
  box-shadow: var(--shadow-sm);
  transform: translateX(4px);
}

.opportunities-list li strong {
  color: var(--color-primary);
}

/* ============================================
   Contact
   ============================================ */
.contact-content {
  max-width: 600px;
}

.contact-links {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  margin: var(--space-md) 0;
}

.contact-link {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--color-text);
  padding: 0.75rem 1rem;
  border-radius: var(--radius-sm);
  transition: color 0.2s ease, background-color 0.2s ease;
}

.contact-link:hover,
.contact-link:focus {
  color: var(--color-accent);
  background-color: var(--color-accent-glow);
}

.contact-link .icon {
  color: var(--color-accent);
}

.contact-also {
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.icon {
  flex-shrink: 0;
}

/* ============================================
   Footer
   ============================================ */
.site-footer {
  background: var(--color-bg-dark);
  padding: var(--space-lg) var(--space-md);
  text-align: center;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.site-footer p {
  font-size: 0.88rem;
  color: rgba(255, 255, 255, 0.45);
  letter-spacing: 0.02em;
}

/* ============================================
   Scroll Animation
   ============================================ */
.animate-on-scroll {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.7s cubic-bezier(0.22, 1, 0.36, 1), transform 0.7s cubic-bezier(0.22, 1, 0.36, 1);
}

.animate-on-scroll.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ============================================
   Responsive — Tablet (768px)
   ============================================ */
@media (max-width: 768px) {
  :root {
    --nav-height: 64px;
  }

  h1 {
    font-size: 2.2rem;
  }

  h2 {
    font-size: 1.65rem;
  }

  .hero {
    padding: var(--space-xl) var(--space-md);
  }

  .hero-content {
    flex-direction: column-reverse;
    text-align: center;
    gap: var(--space-lg);
  }

  .hero-tagline {
    max-width: 100%;
  }

  .hero-image img {
    width: 200px;
    height: 200px;
  }

  .section-inner h2::after {
    left: 0;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-menu {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: var(--space-xs) var(--space-md) var(--space-md);
    gap: 0;
    box-shadow: var(--shadow-lg);
  }

  .nav-menu.open {
    display: flex;
  }

  .nav-menu a {
    padding: 0.75rem 1rem;
    text-align: left;
    font-size: 0.95rem;
  }

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

  .publication-card {
    flex-direction: column;
    gap: var(--space-sm);
  }

  .publication-year {
    width: fit-content;
  }
}

/* ============================================
   Responsive — Small Mobile (480px)
   ============================================ */
@media (max-width: 480px) {
  h1 {
    font-size: 1.85rem;
  }

  h2 {
    font-size: 1.4rem;
  }

  .hero-tagline {
    font-size: 1.05rem;
  }

  .hero-image img {
    width: 160px;
    height: 160px;
  }

  .hero {
    padding: var(--space-lg) var(--space-sm);
  }

  .section {
    padding: var(--space-lg) var(--space-sm);
  }

  .btn {
    width: 100%;
    text-align: center;
  }

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

  .opportunities-list li {
    padding: var(--space-sm);
  }
}

/* ============================================
   Responsive — Large Screens (1200px+)
   ============================================ */
@media (min-width: 1200px) {
  body {
    font-size: 1.1rem;
  }

  h1 {
    font-size: 3.6rem;
  }

  .hero {
    padding: var(--space-2xl) var(--space-md) calc(var(--space-2xl) + 1rem);
  }

  .hero-image img {
    width: 300px;
    height: 300px;
  }
}