:root {
  --bg-color: #fafafa;
  --surface-color: #ffffff;
  --border-color: rgba(0, 0, 0, 0.1);
  --text-primary: #111111;
  --text-secondary: #555555;
  --primary-color: #0097a7;
  --accent-color: #5e35b1;
  --gradient-main: linear-gradient(135deg, var(--accent-color) 0%, var(--primary-color) 100%);
  --font-main: 'Inter', system-ui, -apple-system, sans-serif;
  --radius-lg: 16px;
  --radius-md: 8px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  
  /* Theme specific variables */
  --hero-gradient: linear-gradient(to right, #111111, #555555);
  --header-bg: rgba(250, 250, 250, 0.85);
  --card-hover-bg: rgba(0, 0, 0, 0.02);
  --card-shadow: 0 12px 40px -10px rgba(0, 0, 0, 0.1);
  --badge-hover-bg: rgba(0, 151, 167, 0.05);
  --badge-shadow: 0 4px 12px rgba(0, 151, 167, 0.1);
  --pre-bg: rgba(0, 0, 0, 0.05);
  --code-bg: rgba(0, 151, 167, 0.1);
  --blockquote-bg: rgba(94, 53, 177, 0.05);
  --btn-hover-color: #fafafa;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-color: #050505;
    --surface-color: rgba(255, 255, 255, 0.03);
    --border-color: rgba(255, 255, 255, 0.08);
    --text-primary: #f8f8f8;
    --text-secondary: #a0a0a0;
    --primary-color: #00e5ff;
    --accent-color: #7c4dff;
    
    --hero-gradient: linear-gradient(to right, #ffffff, #a0a0a0);
    --header-bg: rgba(5, 5, 5, 0.85);
    --card-hover-bg: rgba(255, 255, 255, 0.05);
    --card-shadow: 0 12px 40px -10px rgba(124, 77, 255, 0.2);
    --badge-hover-bg: rgba(0, 229, 255, 0.05);
    --badge-shadow: 0 4px 12px rgba(0, 229, 255, 0.1);
    --pre-bg: rgba(0, 0, 0, 0.5);
    --code-bg: rgba(0, 229, 255, 0.1);
    --blockquote-bg: rgba(124, 77, 255, 0.05);
    --btn-hover-color: #050505;
  }
}

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

body {
  font-family: var(--font-main);
  background-color: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Header */
.site-header {
  padding: 24px 0;
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--header-bg);
}

.site-header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-weight: 800;
  font-size: 1.25rem;
  text-decoration: none;
  background: var(--gradient-main);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.5px;
}

nav a {
  color: var(--text-secondary);
  text-decoration: none;
  margin-left: 24px;
  font-size: 0.95rem;
  font-weight: 500;
  transition: var(--transition);
}
nav a:hover {
  color: var(--text-primary);
}

/* Hero */
.hero {
  padding: 100px 0 60px;
  text-align: center;
}

.hero h1 {
  font-size: 4rem;
  font-weight: 800;
  line-height: 1.1;
  margin-bottom: 24px;
  letter-spacing: -1.5px;
  background: var(--hero-gradient);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  max-width: 650px;
  margin: 0 auto;
}

/* Skills */
.skills-section {
  padding: 40px 0 80px;
}
.skills-section h2, .cases-section h2 {
  font-size: 2rem;
  margin-bottom: 40px;
  font-weight: 700;
  text-align: center;
}
.skills-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
}
.skill-badge {
  background: var(--surface-color);
  border: 1px solid var(--border-color);
  padding: 10px 20px;
  border-radius: 100px;
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: var(--transition);
  cursor: default;
}
.skill-badge:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
  background: var(--badge-hover-bg);
  transform: translateY(-2px);
  box-shadow: var(--badge-shadow);
}

/* Cases Grid */
.cases-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
  padding-bottom: 80px;
}

.case-card {
  text-decoration: none;
  background: var(--surface-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 32px;
  display: flex;
  flex-direction: column;
  transition: var(--transition);
  height: 100%;
}

.case-card:hover {
  transform: translateY(-6px);
  border-color: var(--accent-color);
  background: var(--card-hover-bg);
  box-shadow: var(--card-shadow);
}

.case-card-content h3 {
  color: var(--text-primary);
  font-size: 1.3rem;
  margin-bottom: 12px;
  font-weight: 600;
  line-height: 1.3;
}
.case-card-content p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 24px;
  flex-grow: 1;
}
.case-tags .tag {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--accent-color);
  font-weight: 700;
}

/* Markdown Case Article */
.project-group {
  margin-bottom: 60px;
}
.project-group h3 {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--primary-color);
  margin-bottom: 24px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 12px;
  display: inline-block;
}

.case-article {
  padding: 60px 0;
}
.case-header {
  margin-bottom: 40px;
  text-align: center;
}
.case-header h1 {
  font-size: 3rem;
  margin-bottom: 16px;
  letter-spacing: -1px;
}

.markdown-body {
  background: var(--surface-color);
  border: 1px solid var(--border-color);
  padding: 48px;
  border-radius: var(--radius-lg);
  font-size: 1.05rem;
}
.markdown-body h1, .markdown-body h2, .markdown-body h3 {
  margin-top: 2em;
  margin-bottom: 1em;
  color: var(--text-primary);
}
.markdown-body h1:first-child { margin-top: 0; }
.markdown-body p { margin-bottom: 1.5em; color: var(--text-secondary); }
.markdown-body ul, .markdown-body ol { margin-bottom: 1.5em; padding-left: 20px; color: var(--text-secondary); }
.markdown-body li { margin-bottom: 0.5em; }
.markdown-body pre {
  background: var(--pre-bg);
  padding: 20px;
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin-bottom: 1.5em;
  border: 1px solid var(--border-color);
  box-shadow: inset 0 2px 4px rgba(0,0,0,0.05);
}
.markdown-body code {
  font-family: 'Fira Code', monospace;
  font-size: 0.9em;
  color: var(--primary-color);
  background: var(--code-bg);
  padding: 2px 6px;
  border-radius: 4px;
}
.markdown-body pre code {
  background: transparent;
  padding: 0;
  color: inherit;
}
.markdown-body blockquote {
  border-left: 4px solid var(--accent-color);
  padding-left: 16px;
  margin-left: 0;
  color: var(--text-secondary);
  font-style: italic;
  background: var(--blockquote-bg);
  padding: 16px;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}
.markdown-body a {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
}
.markdown-body a:hover {
  text-decoration: underline;
  color: var(--text-primary);
}
.markdown-body img {
  max-width: 100%;
  border-radius: var(--radius-md);
  margin: 20px 0;
}

.case-footer {
  margin-top: 40px;
  text-align: center;
}
.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 28px;
  background: var(--surface-color);
  color: var(--text-primary);
  text-decoration: none;
  border-radius: 100px;
  font-weight: 600;
  border: 1px solid var(--border-color);
  transition: var(--transition);
}
.btn-back:hover {
  background: var(--text-primary);
  color: var(--btn-hover-color);
  transform: translateY(-2px);
}

.site-footer {
  padding: 40px 0;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.9rem;
  border-top: 1px solid var(--border-color);
}

/* Timeline */
.timeline-section {
    padding: 60px 0;
}
.timeline-section h2 {
    font-size: 2.2rem;
    margin-bottom: 50px;
    text-align: center;
}
.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
    padding: 20px 0;
}
.timeline::after {
    content: '';
    position: absolute;
    width: 2px;
    background-color: var(--border-color);
    top: 0;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
}
.timeline-item {
    padding: 10px 40px;
    position: relative;
    width: 50%;
}
.timeline-item:nth-child(even) {
    left: 50%;
}
.timeline-item:nth-child(odd) {
    left: 0;
}
.timeline-dot {
    position: absolute;
    width: 20px;
    height: 20px;
    right: -10px;
    background-color: var(--primary-color);
    border: 4px solid var(--bg-color);
    top: 24px;
    border-radius: 50%;
    z-index: 1;
    box-shadow: 0 0 10px rgba(0, 229, 255, 0.4);
}
.timeline-item:nth-child(even) .timeline-dot {
    left: -10px;
}
.timeline-content {
    padding: 24px;
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--card-shadow);
    transition: var(--transition);
}
.timeline-content:hover {
    transform: translateY(-4px);
    border-color: var(--primary-color);
    box-shadow: 0 10px 30px rgba(0, 229, 255, 0.15);
}
.timeline-content h3 {
    margin-bottom: 8px;
    color: var(--text-primary);
    font-size: 1.35rem;
}
.timeline-content p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}
@media screen and (max-width: 768px) {
  .timeline::after { left: 31px; }
  .timeline-item { width: 100%; padding-left: 70px; padding-right: 25px; }
  .timeline-item:nth-child(even) { left: 0%; }
  .timeline-item:nth-child(even) .timeline-dot, .timeline-item:nth-child(odd) .timeline-dot { left: 21px; }
}

/* Hero CTAs */
.hero-ctas { margin-top: 32px; display: flex; justify-content: center; gap: 16px; flex-wrap: wrap; }
.btn { padding: 12px 28px; border-radius: 100px; font-weight: 600; text-decoration: none; transition: var(--transition); border: 1px solid transparent; }
.btn-primary { background: var(--gradient-main); color: #fff; box-shadow: 0 4px 15px rgba(0, 229, 255, 0.3); }
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(0, 229, 255, 0.4); opacity: 0.9; color: #fff; }
.btn-secondary { background: var(--surface-color); color: var(--text-primary); border-color: var(--border-color); }
.btn-secondary:hover { background: var(--card-hover-bg); border-color: var(--primary-color); color: var(--primary-color); transform: translateY(-2px); }

/* Education Section */
.education-section { padding: 60px 0; }
.education-section h2 { text-align: center; font-size: 2.2rem; margin-bottom: 50px; }
.education-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 24px; max-width: 900px; margin: 0 auto; padding: 0 24px;}
.edu-card { background: var(--surface-color); border: 1px solid var(--border-color); border-radius: var(--radius-md); padding: 30px; transition: var(--transition); text-align: left; }
.edu-card:hover { border-color: var(--primary-color); transform: translateY(-4px); box-shadow: var(--card-shadow); }
.edu-date { display: inline-block; font-size: 0.85rem; color: var(--accent-color); font-weight: 700; margin-bottom: 12px; letter-spacing: 1px; }
.edu-card h3 { font-size: 1.25rem; margin-bottom: 8px; color: var(--text-primary); }
.edu-card p { font-size: 0.95rem; color: var(--text-secondary); line-height: 1.5; }
.edu-card strong { color: var(--primary-color); }

/* Filter Bar */
.filter-bar { display: flex; justify-content: center; gap: 12px; margin-bottom: 50px; flex-wrap: wrap; }
.filter-btn { background: var(--surface-color); border: 1px solid var(--border-color); color: var(--text-secondary); padding: 8px 18px; border-radius: 100px; cursor: pointer; font-family: inherit; font-size: 0.9rem; font-weight: 600; transition: var(--transition); }
.filter-btn:hover { background: var(--card-hover-bg); color: var(--text-primary); border-color: var(--primary-color); }
.filter-btn.active { background: var(--code-bg); color: var(--primary-color); border-color: var(--primary-color); }

/* Language Switch */
.lang-switch { display: inline-flex; align-items: center; gap: 8px; margin-left: 16px; border-left: 1px solid var(--border-color); padding-left: 16px; }
.lang-switch a { font-size: 1.2rem; opacity: 0.5; transition: var(--transition); text-decoration: none; filter: grayscale(1); }
.lang-switch a:hover { opacity: 0.8; filter: grayscale(0.5); transform: translateY(-2px); text-decoration: none; }
.lang-switch a.active { opacity: 1; filter: grayscale(0); }

/* Fade-In Scroll Animations */
.fade-in-section {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease-out, transform 0.8s ease-out;
    will-change: opacity, transform;
}
.fade-in-section.is-visible {
    opacity: 1;
    transform: none;
}

/* Pre-Footer CTA */
.pre-footer-cta { text-align: center; padding: 60px 20px; border-top: 1px solid var(--border-color); margin-top: 40px; }
.pre-footer-cta h2 { margin-bottom: 24px; font-size: 2rem; color: var(--text-primary); }
.pre-footer-cta .btn { font-size: 1.1rem; padding: 14px 28px; }

/* --- Mobile First & Responsive Overrides --- */
@media screen and (max-width: 768px) {
  /* Header */
  .site-header .container { flex-direction: column; gap: 16px; }
  nav { display: flex; flex-wrap: wrap; justify-content: center; gap: 12px; }
  nav a { margin-left: 0; font-size: 0.95rem; }
  .lang-switch { margin-left: 0; border-left: none; padding-left: 0; width: 100%; justify-content: center; margin-top: 8px; }

  /* Hero */
  .hero { padding: 60px 0 30px; }
  .hero h1 { font-size: 2.5rem; }
  .subtitle { font-size: 1.05rem; padding: 0 16px; }
  .hero-ctas { flex-direction: column; padding: 0 16px; }
  .btn { width: 100%; text-align: center; }

  /* General Typography */
  .skills-section h2, .cases-section h2, .timeline-section h2, .education-section h2 { font-size: 1.75rem; }

  /* Project/Case Details */
  .case-header h1 { font-size: 2rem; }
  .markdown-body { padding: 24px 16px; font-size: 1rem; }
  .markdown-body pre { padding: 12px; font-size: 0.85rem; }

  /* Pre-Footer */
  .pre-footer-cta h2 { font-size: 1.5rem; padding: 0 16px; }
}