/* ================================================================
   DESIGN SYSTEM — Academic Research Site
   Colors: Dark Blue + White + Gray
   Fonts: Playfair Display (titles) + Inter (body)
   ================================================================ */

@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@0,400;0,500;0,600;0,700;0,800;1,400;1,500&family=Inter:wght@300;400;500;600;700&display=swap');

/* ── CSS Custom Properties ─────────────────────────────────── */
:root {
  /* Colors */
  --color-bg-primary:    #060e1a;
  --color-bg-secondary:  #0b1930;
  --color-bg-tertiary:   #0f2240;
  --color-bg-card:       rgba(15, 34, 64, 0.6);
  --color-bg-card-hover: rgba(20, 45, 85, 0.8);
  --color-surface:       rgba(255, 255, 255, 0.03);

  --color-text-primary:   #f0f2f5;
  --color-text-secondary: #a0aec0;
  --color-text-muted:     #64748b;

  --color-accent:        #c9a84c;
  --color-accent-light:  #dfc070;
  --color-accent-dim:    rgba(201, 168, 76, 0.15);

  --color-border:        rgba(255, 255, 255, 0.06);
  --color-border-accent: rgba(201, 168, 76, 0.25);

  /* Typography */
  --font-heading: 'Playfair Display', Georgia, 'Times New Roman', serif;
  --font-body:    'Inter', 'Open Sans', -apple-system, sans-serif;

  /* Spacing */
  --space-xs:  0.25rem;
  --space-sm:  0.5rem;
  --space-md:  1rem;
  --space-lg:  1.5rem;
  --space-xl:  2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;
  --space-5xl: 8rem;

  /* Layout */
  --container-max: 1100px;
  --container-narrow: 800px;

  /* Radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 16px;

  /* Transitions */
  --ease-smooth: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --duration-fast: 200ms;
  --duration-normal: 350ms;
  --duration-slow: 600ms;

  /* Shadows */
  --shadow-sm:   0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md:   0 4px 20px rgba(0, 0, 0, 0.4);
  --shadow-lg:   0 8px 40px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 30px rgba(201, 168, 76, 0.08);
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 400;
  line-height: 1.75;
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  overflow-x: hidden;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-smooth);
}

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

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

ul, ol {
  list-style: none;
}

/* ── Typography ────────────────────────────────────────────── */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 600;
  line-height: 1.25;
  color: var(--color-text-primary);
}

h1 {
  font-size: clamp(2.2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

h2 {
  font-size: clamp(1.6rem, 3.5vw, 2.4rem);
  font-weight: 600;
  letter-spacing: -0.01em;
}

h3 {
  font-size: clamp(1.15rem, 2vw, 1.5rem);
  font-weight: 600;
}

h4 {
  font-size: 1.1rem;
  font-weight: 500;
}

p {
  color: var(--color-text-secondary);
  margin-bottom: var(--space-md);
}

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

.text-accent {
  color: var(--color-accent);
}

.text-muted {
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

/* ── Layout ────────────────────────────────────────────────── */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.container--narrow {
  max-width: var(--container-narrow);
}

.section {
  padding: var(--space-5xl) 0;
  position: relative;
}

.section--compact {
  padding: var(--space-3xl) 0;
}

/* Background Utilities */
.bg-primary {
  background-color: var(--color-bg-primary);
}

.bg-secondary {
  background-color: var(--color-bg-secondary);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

/* Section headers */
.section-label {
  font-family: var(--font-body);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: var(--space-md);
}

.section-title {
  margin-bottom: var(--space-lg);
}

.section-subtitle {
  color: var(--color-text-secondary);
  font-size: 1.05rem;
  max-width: 640px;
  line-height: 1.8;
}

.section-divider {
  width: 50px;
  height: 1px;
  background: var(--color-accent);
  margin: var(--space-xl) 0;
  opacity: 0.5;
}

/* ── Navigation ────────────────────────────────────────────── */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  padding: var(--space-lg) 0;
  transition: all var(--duration-normal) var(--ease-smooth);
}

.navbar.scrolled {
  background: rgba(6, 14, 26, 0.92);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--color-border);
}

.navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.navbar__logo {
  font-family: var(--font-heading);
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--color-text-primary);
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  white-space: nowrap;
}

.navbar__logo .logo-symbol {
  color: var(--color-accent);
  font-size: 1.6rem;
}

.navbar__links {
  display: flex;
  align-items: center;
  gap: clamp(var(--space-md), 2vw, var(--space-2xl));
}

.navbar__link {
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-secondary);
  position: relative;
  padding: var(--space-xs) 0;
  transition: color var(--duration-fast) var(--ease-smooth);
}

.navbar__link::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 1px;
  background: var(--color-accent);
  transition: width var(--duration-normal) var(--ease-smooth);
}

.navbar__link:hover,
.navbar__link.active {
  color: var(--color-text-primary);
}

.navbar__link:hover::after,
.navbar__link.active::after {
  width: 100%;
}

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

.navbar__toggle span {
  display: block;
  width: 24px;
  height: 1.5px;
  background: var(--color-text-primary);
  transition: all var(--duration-normal) var(--ease-smooth);
  transform-origin: center;
}

.navbar__toggle.open span:nth-child(1) {
  transform: rotate(45deg) translate(4px, 5px);
}

.navbar__toggle.open span:nth-child(2) {
  opacity: 0;
}

.navbar__toggle.open span:nth-child(3) {
  transform: rotate(-45deg) translate(4px, -5px);
}

/* ── Hero ──────────────────────────────────────────────────── */
.hero {
  position: relative;
  min-height: 75vh;
  display: flex;
  align-items: flex-start;
  overflow: hidden;
  background: var(--color-bg-primary);
  padding-top: 180px;
}

.hero--small {
  min-height: 50vh;
}

.hero__bg {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  opacity: 0.55;
}

.hero__canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  opacity: 0.4;
}

.hero__overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(
    180deg,
    rgba(6, 14, 26, 0.15) 0%,
    rgba(6, 14, 26, 0.45) 45%,
    var(--color-bg-primary) 100%
  );
  z-index: 1;
}

.hero__content {
  position: relative;
  z-index: 2;
  max-width: var(--container-narrow);
  margin: 0 auto;
  padding: 0 var(--space-xl);
  padding-top: 0;
}

.hero__label {
  font-family: var(--font-body);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: var(--space-lg);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.hero__label::before {
  content: '';
  width: 30px;
  height: 1px;
  background: var(--color-accent);
}

.hero__title {
  margin-bottom: var(--space-xl);
  max-width: 1200px;
  font-size: clamp(1.8rem, 3.2vw, 2.8rem) !important;
}

.hero__description {
  font-size: 1.1rem;
  line-height: 1.9;
  color: var(--color-text-secondary);
  max-width: 620px;
}

/* ── Cards ─────────────────────────────────────────────────── */
.card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-2xl);
  transition: all var(--duration-normal) var(--ease-smooth);
  position: relative;
  overflow: hidden;
}

.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--color-accent), transparent);
  opacity: 0;
  transition: opacity var(--duration-normal) var(--ease-smooth);
}

.card:hover {
  background: var(--color-bg-card-hover);
  border-color: var(--color-border-accent);
  transform: translateY(-3px);
  box-shadow: var(--shadow-glow);
}

.card:hover::before {
  opacity: 1;
}

.card__icon {
  font-size: 1.5rem;
  margin-bottom: var(--space-lg);
  color: var(--color-accent);
}

.card__title {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  margin-bottom: var(--space-md);
  color: var(--color-text-primary);
}

.card__text {
  color: var(--color-text-secondary);
  font-size: 0.925rem;
  line-height: 1.75;
}

/* Grid layouts */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-xl);
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-xl);
}

/* ── Badge ─────────────────────────────────────────────────── */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: var(--space-xs) var(--space-md);
  border-radius: 100px;
  background: var(--color-accent-dim);
  color: var(--color-accent);
  border: 1px solid var(--color-border-accent);
}

.badge--muted {
  background: rgba(255, 255, 255, 0.04);
  color: var(--color-text-muted);
  border-color: var(--color-border);
}

/* ── Buttons ───────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 500;
  letter-spacing: 0.06em;
  padding: var(--space-md) var(--space-2xl);
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  transition: all var(--duration-normal) var(--ease-smooth);
  text-transform: uppercase;
}

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

.btn--primary:hover {
  background: var(--color-accent-light);
  color: var(--color-bg-primary);
  transform: translateY(-2px);
  box-shadow: 0 4px 20px rgba(201, 168, 76, 0.25);
}

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

.btn--outline:hover {
  background: var(--color-accent-dim);
  border-color: var(--color-accent);
  transform: translateY(-2px);
}

.btn--text {
  background: none;
  color: var(--color-accent);
  padding: 0;
  letter-spacing: 0.04em;
  font-weight: 500;
}

.btn--text:hover {
  color: var(--color-accent-light);
}

.btn--text .arrow {
  transition: transform var(--duration-fast) var(--ease-smooth);
}

.btn--text:hover .arrow {
  transform: translateX(4px);
}

/* ── Footer ────────────────────────────────────────────────── */
.footer {
  border-top: 1px solid var(--color-border);
  padding: var(--space-3xl) 0 var(--space-2xl);
  background: var(--color-bg-primary);
}

.footer__inner {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--space-2xl);
}

.footer__logo {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--space-md);
  white-space: nowrap;
}

.footer__text {
  color: var(--color-text-muted);
  font-size: 0.8rem;
  max-width: 400px;
  line-height: 1.7;
}

.footer__links {
  display: flex;
  gap: var(--space-xl);
}

.footer__link {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  font-weight: 500;
}

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

.footer__socials {
  margin-top: var(--space-md);
  display: flex;
  gap: var(--space-md);
}

.footer__social-link {
  color: var(--color-text-muted);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: color var(--duration-fast) var(--ease-smooth);
}

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

.footer__bottom {
  margin-top: var(--space-2xl);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer__copyright {
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

.footer__disclaimer {
  font-size: 0.7rem;
  color: var(--color-text-muted);
  max-width: 500px;
  text-align: right;
  line-height: 1.6;
}

/* ── Scroll Reveal Animation ───────────────────────────────── */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity var(--duration-slow) var(--ease-smooth),
              transform var(--duration-slow) var(--ease-smooth);
}

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

.reveal-delay-1 { transition-delay: 100ms; }
.reveal-delay-2 { transition-delay: 200ms; }
.reveal-delay-3 { transition-delay: 300ms; }
.reveal-delay-4 { transition-delay: 400ms; }
.reveal-delay-5 { transition-delay: 500ms; }

/* ── Separator line ────────────────────────────────────────── */
.separator {
  width: 100%;
  height: 1px;
  background: var(--color-border);
}

/* ── Approach / Principles ─────────────────────────────────── */
.approach {
}

.principles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-2xl);
}

.principle {
  text-align: center;
  padding: var(--space-2xl) var(--space-lg);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: all var(--duration-normal) var(--ease-smooth);
}

.principle:hover {
  border-color: var(--color-border-accent);
  transform: translateY(-4px);
  box-shadow: var(--shadow-glow);
}

.principle__icon {
  font-size: 1.8rem;
  margin-bottom: var(--space-lg);
  display: block;
}

.principle__title {
  font-family: var(--font-heading);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text-primary);
  margin-bottom: var(--space-sm);
}

.principle__line {
  width: 24px;
  height: 1px;
  background: var(--color-accent);
  margin: var(--space-md) auto;
  opacity: 0.5;
}

.principle__desc {
  font-size: 0.825rem;
  color: var(--color-text-muted);
  line-height: 1.7;
}

/* ── Responsive ────────────────────────────────────────────── */
@media (max-width: 768px) {
  .navbar__links {
    position: fixed;
    top: 0;
    right: -100%;
    width: 280px;
    height: 100vh;
    flex-direction: column;
    justify-content: center;
    background: rgba(6, 14, 26, 0.98);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    gap: var(--space-xl);
    transition: right var(--duration-normal) var(--ease-smooth);
    border-left: 1px solid var(--color-border);
  }

  .navbar__links.open {
    right: 0;
  }

  .navbar__toggle {
    display: flex;
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }

  .hero {
    min-height: 75vh;
    align-items: flex-start;
    padding-top: 140px;
  }

  .hero--small {
    min-height: 40vh;
  }

  .section {
    padding: var(--space-3xl) 0;
  }

  .container {
    padding: 0 var(--space-lg);
  }

  .footer__inner {
    flex-direction: column;
  }

  .footer__bottom {
    flex-direction: column;
    gap: var(--space-md);
    text-align: center;
  }

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

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

@media (max-width: 480px) {
  h1 {
    font-size: 1.8rem;
  }

  .hero__description {
    font-size: 1rem;
  }

  .principles-grid {
    grid-template-columns: 1fr;
  }
}