/* ===== Custom Properties ===== */
:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f8f9fa;
  --color-bg-card: #ffffff;
  --color-text: #1a1a2e;
  --color-text-muted: #555b6e;
  --color-primary: #2c3e50;
  --color-accent: #3498db;
  --color-accent-hover: #2980b9;
  --color-border: #e0e0e0;
  --color-tag-bg: #eef2f7;
  --color-tag-text: #2c3e50;
  --color-hero-bg: #1a1a2e;
  --color-hero-text: #f0f0f0;
  --color-footer-bg: #1a1a2e;
  --color-footer-text: #c8c8d0;
  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --max-width: 1100px;
  --section-padding: 5rem 1.5rem;
  --radius: 8px;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
  --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.1);
  --transition: 0.25s ease;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0f0f1a;
    --color-bg-alt: #1a1a2e;
    --color-bg-card: #1e1e32;
    --color-text: #e4e4ed;
    --color-text-muted: #9a9ab0;
    --color-primary: #c8c8d0;
    --color-accent: #5dade2;
    --color-accent-hover: #85c1e9;
    --color-border: #2e2e45;
    --color-tag-bg: #2a2a40;
    --color-tag-text: #c8c8d0;
    --color-hero-bg: #0a0a14;
    --color-hero-text: #e4e4ed;
    --color-footer-bg: #0a0a14;
    --color-footer-text: #9a9ab0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.4);
  }
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

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

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

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

ul, ol {
  list-style: none;
}

/* ===== Typography ===== */
h1, h2, h3, h4 {
  color: var(--color-primary);
  line-height: 1.3;
  font-weight: 700;
}

h1 {
  font-size: clamp(2.2rem, 5vw, 3.2rem);
}

h2 {
  font-size: clamp(1.6rem, 3vw, 2rem);
}

h3 {
  font-size: clamp(1.1rem, 2vw, 1.3rem);
}

/* ===== Layout Utilities ===== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  width: 100%;
}

.section {
  padding: var(--section-padding);
}

.section-title {
  margin-bottom: 2.5rem;
  position: relative;
  display: inline-block;
}

.section-title::after {
  content: '';
  display: block;
  width: 50px;
  height: 3px;
  background: var(--color-accent);
  margin-top: 0.5rem;
  border-radius: 2px;
}

/* Fade-in animation */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* ===== Navigation ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  transition: box-shadow var(--transition);
}

.navbar.scrolled {
  box-shadow: var(--shadow);
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  height: 64px;
}

.nav-brand {
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--color-primary);
  letter-spacing: -0.02em;
}

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

.nav-links {
  display: flex;
  gap: 2rem;
  align-items: center;
}

.nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text-muted);
  transition: color var(--transition);
  position: relative;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--color-accent);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  color: var(--color-text);
}

.nav-toggle svg {
  width: 24px;
  height: 24px;
  stroke: currentColor;
  fill: none;
  stroke-width: 2;
  stroke-linecap: round;
}

/* ===== Hero ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-hero-bg);
  color: var(--color-hero-text);
  padding: 6rem 1.5rem 4rem;
  text-align: center;
}

.hero h1 {
  color: #ffffff;
  margin-bottom: 0.5rem;
}

.hero-tagline {
  font-size: clamp(1rem, 2.5vw, 1.25rem);
  color: var(--color-accent);
  font-weight: 500;
  margin-bottom: 1.25rem;
  font-family: var(--font-mono);
}

.hero-summary {
  font-size: clamp(1rem, 2vw, 1.1rem);
  color: var(--color-hero-text);
  max-width: 600px;
  margin: 0 auto 2rem;
  opacity: 0.85;
}

.hero-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.75rem;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 0.95rem;
  transition: all var(--transition);
  cursor: pointer;
  border: 2px solid transparent;
}

.btn-primary {
  background: var(--color-accent);
  color: #ffffff;
  border-color: var(--color-accent);
}

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

.btn-outline {
  background: transparent;
  color: #ffffff;
  border-color: rgba(255, 255, 255, 0.4);
}

.btn-outline:hover {
  border-color: #ffffff;
  color: #ffffff;
}

.hero-socials {
  display: flex;
  gap: 1.25rem;
  justify-content: center;
}

.hero-socials a {
  color: rgba(255, 255, 255, 0.6);
  transition: color var(--transition), transform var(--transition);
}

.hero-socials a:hover {
  color: #ffffff;
  transform: translateY(-2px);
}

.hero-socials svg {
  width: 22px;
  height: 22px;
}

/* ===== About ===== */
.about {
  background: var(--color-bg-alt);
}

.about-content {
  max-width: 750px;
  font-size: 1.05rem;
  color: var(--color-text-muted);
  line-height: 1.8;
}

/* ===== Work Experience ===== */
.timeline {
  position: relative;
  padding-left: 2rem;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-bottom: 2.5rem;
}

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

.timeline-item::before {
  content: '';
  position: absolute;
  left: -2rem;
  top: 0.35rem;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-accent);
  border: 2px solid var(--color-bg);
  transform: translateX(-5px);
}

.timeline-header {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.5rem 1rem;
  margin-bottom: 0.5rem;
}

.timeline-header h3 {
  color: var(--color-primary);
}

.timeline-company {
  font-weight: 600;
  color: var(--color-accent);
}

.timeline-meta {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

.timeline-bullets {
  padding-left: 1.25rem;
  list-style: disc;
}

.timeline-bullets li {
  margin-bottom: 0.4rem;
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

/* ===== Skills ===== */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.skill-category {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: box-shadow var(--transition);
}

.skill-category:hover {
  box-shadow: var(--shadow-hover);
}

.skill-category h3 {
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-accent);
  margin-bottom: 0.75rem;
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.skill-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  background: var(--color-tag-bg);
  color: var(--color-tag-text);
  padding: 0.35rem 0.75rem;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 500;
}

.skill-tag .years {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

/* ===== Projects ===== */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.25rem;
}

.project-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  transition: box-shadow var(--transition), transform var(--transition);
}

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

.project-card h3 {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.project-card h3 svg {
  width: 20px;
  height: 20px;
  color: var(--color-text-muted);
  flex-shrink: 0;
}

.project-card h3 a {
  color: var(--color-primary);
  font-weight: 600;
}

.project-card h3 a:hover {
  color: var(--color-accent);
}

.project-description {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  flex-grow: 1;
  margin-bottom: 1rem;
}

.project-meta {
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.project-lang {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}

.lang-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  display: inline-block;
}

.project-stars {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}

.project-stars svg {
  width: 14px;
  height: 14px;
}

.projects-loading,
.projects-error {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--color-text-muted);
}

.projects-link {
  text-align: center;
  margin-top: 2rem;
}

.projects-link a {
  font-weight: 600;
  font-size: 0.95rem;
}

/* ===== Education ===== */
.education-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  max-width: 500px;
}

.education-card h3 {
  margin-bottom: 0.25rem;
}

.education-card .school {
  color: var(--color-accent);
  font-weight: 600;
  font-size: 0.95rem;
}

/* ===== Contact ===== */
.contact {
  background: var(--color-bg-alt);
  text-align: center;
}

.contact-text {
  color: var(--color-text-muted);
  max-width: 500px;
  margin: 0 auto 2rem;
  font-size: 1.05rem;
}

.contact-links {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.contact-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1.25rem;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-weight: 500;
  font-size: 0.9rem;
  color: var(--color-text);
  transition: all var(--transition);
}

.contact-link:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  box-shadow: var(--shadow);
}

.contact-link svg {
  width: 18px;
  height: 18px;
}

/* ===== Footer ===== */
.footer {
  background: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: 2rem 1.5rem;
  text-align: center;
  font-size: 0.85rem;
}

.footer .container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.footer-socials {
  display: flex;
  gap: 1rem;
}

.footer-socials a {
  color: var(--color-footer-text);
  transition: color var(--transition);
}

.footer-socials a:hover {
  color: #ffffff;
}

.footer-socials svg {
  width: 18px;
  height: 18px;
}

/* ===== Mobile Navigation ===== */
@media (max-width: 768px) {
  .nav-toggle {
    display: block;
  }

  .nav-links {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--color-bg);
    flex-direction: column;
    padding: 1.5rem;
    gap: 1rem;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.3s ease, opacity 0.3s ease;
  }

  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .nav-links a {
    font-size: 1rem;
    padding: 0.5rem 0;
  }

  .hero {
    min-height: auto;
    padding: 7rem 1.5rem 3rem;
  }

  .section {
    padding: 3rem 1.25rem;
  }

  .timeline {
    padding-left: 1.5rem;
  }

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

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

@media (max-width: 480px) {
  .hero-buttons {
    flex-direction: column;
    align-items: center;
  }

  .btn {
    width: 100%;
    justify-content: center;
    max-width: 280px;
  }

  .contact-links {
    flex-direction: column;
    align-items: center;
  }
}