:root {
  --bg: #ffffff;
  --bg-secondary: #f5f7fa;
  --text: #1a1a2e;
  --text-secondary: #4a4a6a;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --header-bg: rgba(255, 255, 255, 0.9);
  --skill-bg: #eef2ff;
  --tag-bg: #e0e7ff;
  --tag-text: #3730a3;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.1);
  --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --max-width: 1100px;
  --radius: 12px;
}

[data-theme="dark"] {
  --bg: #0f172a;
  --bg-secondary: #1e293b;
  --text: #e2e8f0;
  --text-secondary: #94a3b8;
  --accent: #60a5fa;
  --accent-hover: #3b82f6;
  --card-bg: #1e293b;
  --border: #334155;
  --header-bg: rgba(15, 23, 42, 0.9);
  --skill-bg: #1e293b;
  --tag-bg: #1e293b;
  --tag-text: #93c5fd;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.4);
  --gradient-hero: linear-gradient(135deg, #1e3a5f 0%, #2d1b69 100%);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background-color 0.3s, color 0.3s;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.2s;
}

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

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

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.section {
  padding: 80px 0;
}

.section:nth-child(even) {
  background-color: var(--bg-secondary);
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 48px;
  text-align: center;
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background: var(--accent);
  margin: 12px auto 0;
  border-radius: 2px;
}

.grid {
  display: grid;
  gap: 24px;
}

.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  transition: transform 0.2s, box-shadow 0.2s;
}

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

.btn {
  display: inline-block;
  padding: 12px 28px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: all 0.2s;
  border: none;
}

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

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

.btn-outline {
  background: transparent;
  border: 2px solid var(--accent);
  color: var(--accent);
}

.btn-outline:hover {
  background: var(--accent);
  color: #fff;
}

.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

@media (max-width: 768px) {
  .section {
    padding: 48px 0;
  }
  .section-title {
    font-size: 1.5rem;
    margin-bottom: 32px;
  }
}