/* ==========================================================================
   CSS Variables
   ========================================================================== */

:root {
  /* Colors */
  --color-bg: #ffffff;
  --color-bg-alt: #fafafa;
  --color-text: #0a0a0a;
  --color-text-secondary: #525252;
  --color-text-muted: #737373;
  --color-border: #e5e5e5;
  --color-border-light: #f0f0f0;
  --color-accent: #171717;
  --color-accent-hover: #404040;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: 2.75rem;
  --font-size-5xl: 3.5rem;
  --line-height: 1.6;
  --line-height-tight: 1.25;

  /* 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;

  /* Layout */
  --container-max: 1100px;
  --header-height: 64px;
  --border-radius: 12px;
  --border-radius-sm: 8px;
  --border-radius-full: 9999px;

  /* Effects */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.08);
  --transition: 0.2s ease;
  --transition-slow: 0.4s ease;
}

/* ==========================================================================
   Reset & Base
   ========================================================================== */

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

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

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  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: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

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

/* ==========================================================================
   Layout
   ========================================================================== */

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

.section {
  padding: var(--space-4xl) 0;
}

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

.section-title {
  font-size: var(--font-size-3xl);
  font-weight: 600;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-2xl);
  line-height: var(--line-height-tight);
}

.section-description {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  max-width: 600px;
  margin-bottom: var(--space-2xl);
}

/* ==========================================================================
   Animations
   ========================================================================== */

.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ==========================================================================
   Navigation
   ========================================================================== */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--header-height);
  background-color: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.site-header.scrolled {
  border-bottom-color: var(--color-border);
  box-shadow: var(--shadow-sm);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav-logo {
  font-size: var(--font-size-lg);
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--color-text);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.nav-link {
  padding: var(--space-sm) var(--space-md);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  border-radius: var(--border-radius-sm);
  transition: color var(--transition), background-color var(--transition);
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-text);
}

.nav-link.active {
  background-color: var(--color-bg-alt);
}

.nav-resume-btn {
  margin-left: var(--space-sm);
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-bg);
  background-color: var(--color-accent);
  border-radius: var(--border-radius-sm);
  transition: background-color var(--transition);
}

.nav-resume-btn:hover {
  background-color: var(--color-accent-hover);
}

/* Mobile menu toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 32px;
  height: 32px;
  padding: 4px;
}

.nav-toggle-bar {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--color-text);
  border-radius: 1px;
  transition: transform var(--transition), opacity var(--transition);
}

.nav-toggle.active .nav-toggle-bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle.active .nav-toggle-bar:nth-child(2) {
  opacity: 0;
}

.nav-toggle.active .nav-toggle-bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.625rem 1.25rem;
  font-size: var(--font-size-sm);
  font-weight: 500;
  border-radius: var(--border-radius-sm);
  transition: background-color var(--transition), color var(--transition), border-color var(--transition);
  white-space: nowrap;
}

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

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

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

.btn-secondary:hover {
  background-color: var(--color-bg-alt);
  border-color: var(--color-text-muted);
}

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

.btn-outline:hover {
  background-color: var(--color-bg-alt);
  border-color: var(--color-text-muted);
}

/* ==========================================================================
   Hero
   ========================================================================== */

.hero {
  padding-top: calc(var(--header-height) + var(--space-4xl));
  padding-bottom: var(--space-3xl);
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: var(--space-3xl);
  align-items: center;
  margin-bottom: var(--space-3xl);
}

.hero-title {
  font-size: var(--font-size-5xl);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: var(--line-height-tight);
  margin-bottom: var(--space-md);
}

.hero-subtitle {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-lg);
}

.hero-description {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  max-width: 520px;
  margin-bottom: var(--space-xl);
  line-height: var(--line-height);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
}

.profile-photo {
  width: 280px;
  height: 280px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--color-border-light);
  box-shadow: var(--shadow-md);
}

/* Stats bar */
.stats-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-lg);
  padding: var(--space-xl);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
}

.stat-item {
  text-align: center;
}

.stat-number {
  display: block;
  font-size: var(--font-size-2xl);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-xs);
}

.stat-label {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* ==========================================================================
   About
   ========================================================================== */

.about-grid {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: var(--space-3xl);
  align-items: start;
}

.about-text p {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  line-height: var(--line-height);
}

.currently-box {
  padding: var(--space-xl);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
}

.currently-title {
  font-size: var(--font-size-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-lg);
}

.currently-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.currently-list li {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.currently-role {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
}

.currently-org {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* ==========================================================================
   Projects
   ========================================================================== */

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: var(--space-xl);
}

.project-card {
  display: flex;
  flex-direction: column;
  padding: var(--space-2xl);
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  transition: box-shadow var(--transition), border-color var(--transition);
}

.project-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-text-muted);
}

.project-card-coming {
  border-style: dashed;
  opacity: 0.7;
}

.project-card-coming:hover {
  box-shadow: none;
  border-color: var(--color-border);
}

.project-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.project-title {
  font-size: var(--font-size-xl);
  font-weight: 600;
  letter-spacing: -0.01em;
}

.project-tag {
  font-size: var(--font-size-xs);
  font-weight: 500;
  padding: var(--space-xs) var(--space-sm);
  color: var(--color-text-secondary);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-full);
  white-space: nowrap;
}

.project-description {
  flex: 1;
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  line-height: var(--line-height);
}

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

/* ==========================================================================
   Experience Timeline
   ========================================================================== */

.timeline {
  position: relative;
  padding-left: var(--space-2xl);
}

.timeline::before {
  content: "";
  position: absolute;
  left: 6px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background-color: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-bottom: var(--space-2xl);
}

.timeline-item:last-child {
  padding-bottom: 0;
}

.timeline-marker {
  position: absolute;
  left: calc(-1 * var(--space-2xl) + 2px);
  top: 8px;
  width: 10px;
  height: 10px;
  background-color: var(--color-bg);
  border: 2px solid var(--color-accent);
  border-radius: 50%;
}

.timeline-card {
  padding: var(--space-xl);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  transition: box-shadow var(--transition);
}

.timeline-card:hover {
  box-shadow: var(--shadow-sm);
}

.timeline-org {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.timeline-role {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.timeline-summary {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  line-height: var(--line-height);
}

/* ==========================================================================
   Research
   ========================================================================== */

.research-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-xl);
}

.research-card {
  padding: var(--space-2xl);
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
}

.research-card-placeholder {
  border-style: dashed;
}

.research-card-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--space-lg);
}

.research-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.research-list li {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  padding-left: var(--space-lg);
  position: relative;
}

.research-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.6em;
  width: 6px;
  height: 6px;
  background-color: var(--color-accent);
  border-radius: 50%;
}

.research-placeholder-text {
  font-size: var(--font-size-base);
  color: var(--color-text-muted);
  font-style: italic;
}

/* ==========================================================================
   Leadership
   ========================================================================== */

.leadership-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-xl);
}

.leadership-card {
  padding: var(--space-xl);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  transition: box-shadow var(--transition), border-color var(--transition);
}

.leadership-card:hover {
  box-shadow: var(--shadow-sm);
  border-color: var(--color-text-muted);
}

.leadership-icon {
  width: 40px;
  height: 40px;
  margin-bottom: var(--space-md);
  color: var(--color-text);
}

.leadership-icon svg {
  width: 100%;
  height: 100%;
}

.leadership-title {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--space-sm);
}

.leadership-text {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: var(--line-height);
}

/* ==========================================================================
   Awards
   ========================================================================== */

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

.award-card {
  padding: var(--space-xl);
  text-align: center;
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  transition: box-shadow var(--transition);
}

.award-card:hover {
  box-shadow: var(--shadow-sm);
}

.award-icon {
  font-size: var(--font-size-2xl);
  margin-bottom: var(--space-md);
}

.award-title {
  font-size: var(--font-size-base);
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.award-text {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* ==========================================================================
   Skills
   ========================================================================== */

.skills-group {
  margin-bottom: var(--space-2xl);
}

.skills-group:last-child {
  margin-bottom: 0;
}

.skills-category {
  font-size: var(--font-size-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.skills-pills {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.skill-pill {
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text);
  background-color: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-full);
  transition: border-color var(--transition), background-color var(--transition);
}

.skill-pill:hover {
  border-color: var(--color-text-muted);
  background-color: var(--color-bg);
}

/* ==========================================================================
   Contact
   ========================================================================== */

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

.contact-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-2xl);
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  transition: box-shadow var(--transition), border-color var(--transition), transform var(--transition);
}

.contact-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-text-muted);
  transform: translateY(-2px);
}

.contact-icon {
  width: 28px;
  height: 28px;
  color: var(--color-text);
}

.contact-label {
  font-size: var(--font-size-sm);
  font-weight: 500;
}

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--color-border);
  text-align: center;
}

.site-footer p {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* ==========================================================================
   Back to Top
   ========================================================================== */

.back-to-top {
  position: fixed;
  bottom: var(--space-xl);
  right: var(--space-xl);
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--color-accent);
  color: var(--color-bg);
  border-radius: var(--border-radius-sm);
  box-shadow: var(--shadow-md);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity var(--transition), visibility var(--transition), transform var(--transition), background-color var(--transition);
  z-index: 900;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background-color: var(--color-accent-hover);
}

.back-to-top svg {
  width: 20px;
  height: 20px;
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (max-width: 900px) {
  .hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .hero-image {
    order: -1;
  }

  .hero-description {
    margin-left: auto;
    margin-right: auto;
  }

  .hero-actions {
    justify-content: center;
  }

  .profile-photo {
    width: 200px;
    height: 200px;
    margin: 0 auto;
  }

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

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

@media (max-width: 768px) {
  :root {
    --font-size-5xl: 2.5rem;
    --font-size-4xl: 2rem;
    --font-size-3xl: 1.75rem;
  }

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

  .nav-toggle {
    display: flex;
  }

  .nav-links {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: var(--space-md);
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition), opacity var(--transition), visibility var(--transition);
  }

  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-link {
    padding: var(--space-md);
    font-size: var(--font-size-base);
  }

  .nav-resume-btn {
    margin-left: 0;
    margin-top: var(--space-sm);
    text-align: center;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-md);
  }

  .stats-bar {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-md);
    padding: var(--space-lg);
  }

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

  .hero-actions .btn {
    width: 100%;
  }

  .project-actions {
    flex-direction: column;
  }

  .project-actions .btn {
    width: 100%;
  }
}

/* ==========================================================================
   Accessibility
   ========================================================================== */

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .fade-in {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .back-to-top,
  .contact-card,
  .project-card,
  .leadership-card {
    transition: none;
  }
}

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