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

:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f7f7f7;
  --color-text: #0a2540;
  --color-text-muted: #425466;
  --color-accent: #0077B6;
  --color-accent-hover: #005f8a;
  --color-border: #e6e9ed;
  --font-body: 'Source Serif 4', Georgia, serif;
  --font-display: 'Source Serif 4', Georgia, serif;
  --max-width: 1100px;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 2rem;
  --spacing-lg: 4rem;
  --spacing-xl: 6rem;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
}

/* Typography */
h1, h2, h3 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.2;
  color: var(--color-text);
}

h1 {
  font-size: clamp(2.5rem, 6vw, 3.5rem);
  letter-spacing: -0.03em;
  font-weight: 600;
}

h2 {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-md);
  letter-spacing: -0.02em;
}

h3 {
  font-size: 1.1rem;
  margin-bottom: var(--spacing-xs);
  font-weight: 600;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.15s;
}

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

.link-hume,
.link-sigma {
  color: var(--color-text);
  text-decoration: underline;
  transition: background-color 0.15s, color 0.15s;
}

.link-hume:hover {
  background-color: #FDB4D5;
  color: var(--color-text);
}

.link-sigma:hover {
  background-color: #F0FF45;
  color: var(--color-text);
}

/* Navigation */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.nav-content {
  max-width: calc(var(--max-width) + var(--spacing-md) * 2);
  margin: 0 auto;
  padding: var(--spacing-sm) var(--spacing-md);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-left {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.nav-left a {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  font-weight: 500;
  transition: color 0.15s;
}

.nav-left a:hover {
  color: var(--color-accent);
}

.logo.logo {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.nav-right {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.nav-right a {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  font-weight: 500;
  transition: color 0.15s;
  display: flex;
  align-items: center;
}

.nav-right a:hover {
  color: var(--color-accent);
}

a.social-github:hover {
  color: #24292e;
}

a.social-linkedin:hover {
  color: #0A66C2;
}

/* Hero */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding: var(--spacing-xl) var(--spacing-md);
}

.hero-content {
  max-width: calc(var(--max-width) + var(--spacing-md) * 2);
  margin: 0 auto;
  width: 100%;
  padding: 0 var(--spacing-md);
}

.hero-greeting {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-xs);
}

.hero-main {
  display: grid;
  grid-template-columns: 1fr 380px;
  gap: var(--spacing-lg);
  align-items: start;
}

.hero-text {
  min-width: 0;
}

.hero-image img {
  width: 100%;
  height: auto;
  border-radius: 12px;
  object-fit: cover;
}

.hero-bio {
  max-width: 640px;
  margin-top: var(--spacing-md);
  margin-bottom: var(--spacing-md);
}

.hero-bio p {
  color: var(--color-text-muted);
  font-size: 1rem;
  margin-bottom: var(--spacing-sm);
  line-height: 1.75;
}

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

.hero-cta {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-top: var(--spacing-md);
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.625rem 1.25rem;
  border-radius: 6px;
  font-size: 0.875rem;
  font-weight: 500;
  transition: all 0.15s;
}

.btn-primary {
  background: var(--color-accent);
  color: #fff;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(2, 132, 199, 0.25);
}

.btn-secondary {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  color: var(--color-text);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

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

/* Sections */
.section {
  padding: var(--spacing-xl) var(--spacing-md);
  max-width: calc(var(--max-width) + var(--spacing-md) * 2);
  margin: 0 auto;
}

.section-alt {
  max-width: none;
  background: var(--color-bg);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
}

.section-alt > h2,
.section-alt > .projects-grid,
.section-alt > .contact-content {
  max-width: calc(var(--max-width) + var(--spacing-md) * 2);
  margin-left: auto;
  margin-right: auto;
  padding: 0 var(--spacing-md);
}

.section-intro {
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-md);
  max-width: 600px;
}

/* Skills */
.about-content {
  display: grid;
  gap: var(--spacing-md);
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--spacing-sm);
}

.skill-card {
  padding: var(--spacing-md);
  background: var(--color-bg);
  border-radius: 12px;
  border: 1px solid var(--color-border);
  transition: box-shadow 0.2s, border-color 0.2s;
}

.skill-card:hover {
  border-color: transparent;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
}

.skill-card h3 {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--color-accent);
  margin-bottom: 0.5rem;
}

.skill-card p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  line-height: 1.6;
}

/* Projects */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-md);
}

.project-card {
  background: var(--color-bg);
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid var(--color-border);
  transition: all 0.2s;
  display: flex;
  flex-direction: column;
}

.project-card:hover {
  border-color: transparent;
  box-shadow: 0 8px 30px rgba(0, 119, 182, 0.15);
}

.project-info {
  padding: var(--spacing-md);
  display: flex;
  flex-direction: column;
  flex: 1;
}

.project-info h3 {
  color: var(--color-text);
}

.project-course {
  display: block;
  font-size: 0.8rem;
  color: var(--color-text-muted);
  min-height: 1.2em;
}

.project-info > p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  line-height: 1.6;
  margin-top: 0.5rem;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.375rem;
  padding-top: var(--spacing-sm);
  padding-bottom: var(--spacing-sm);
}

.project-tags span {
  font-size: 0.75rem;
  padding: 0.25rem 0.625rem;
  background: #E7F5FD;
  border-radius: 4px;
  color: var(--color-accent);
  font-weight: 500;
}

.project-links {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-top: auto;
  padding-top: var(--spacing-sm);
  border-top: 1px solid var(--color-border);
}

.project-links a {
  color: var(--color-text-muted);
  transition: color 0.15s;
  display: flex;
  align-items: center;
}

.project-links a.social-github:hover {
  color: #24292e;
}

.project-btn {
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.375rem 0.75rem;
  background: #fff;
  color: #000 !important;
  border: 1px solid #000;
  border-radius: 4px;
  transition: background 0.15s, color 0.15s;
}

.project-links .social-github {
  margin-left: auto;
}

.project-btn:hover {
  background: #fff;
  color: var(--color-accent) !important;
  border-color: var(--color-accent);
}

/* Research */
.research-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
}

.research-item {
  display: grid;
  grid-template-columns: 60px 1fr;
  gap: var(--spacing-md);
  padding: var(--spacing-sm) 0;
  border-bottom: 1px solid var(--color-border);
}

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

.research-date {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

.research-content h3 {
  font-family: var(--font-body);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 0.25rem;
}

.research-course {
  display: block;
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.research-content p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  line-height: 1.6;
}

.research-link {
  color: var(--color-text);
  display: inline-flex;
  align-items: baseline;
  gap: 0.4rem;
}

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

.research-link svg {
  flex-shrink: 0;
  position: relative;
  top: 2px;
}


/* Footer */
.footer {
  padding: var(--spacing-lg) var(--spacing-md);
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.8rem;
}

/* Responsive */
@media (max-width: 768px) {
  .hero-main {
    grid-template-columns: 1fr;
  }

  .hero-image {
    order: -1;
    max-width: 200px;
  }

  .nav-right {
    gap: var(--spacing-sm);
  }

  .research-item {
    grid-template-columns: 1fr;
    gap: var(--spacing-xs);
  }

  .research-date {
    font-size: 0.85rem;
  }
}

@media (max-width: 480px) {
  .nav-right a:not(.social-github):not(.social-linkedin) {
    display: none;
  }

  .hero {
    min-height: auto;
    padding-top: 120px;
  }
}