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

/* Light Mode (Default) */
:root {
  --bg: #f8f9fa;
  --text: #1a1a1a;
  --card-bg: #ffffff;
  --header-bg: #ffffff;
  --border: #e0e0e0;
  --accent: #0066ff;
}

/* Dark Mode */
[data-theme="dark"] {
  --bg: #0f0f0f;
  --text: #ffffff;
  --card-bg: #1a1a1a;
  --header-bg: #1a1a1a;
  --border: #333;
  --accent: #4d9fff;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background 0.3s;
}

header {
  background: var(--header-bg);
  padding: 1.5rem 5%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border);
}

h1 {
  font-size: 1.8rem;
}

nav a {
  color: var(--text);
  text-decoration: none;
  margin-left: 2rem;
  font-weight: 500;
}

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

.theme-btn {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  margin-left: 1rem;
}

main {
  padding: 4rem 5%;
  max-width: 1200px;
  margin: 0 auto;
}

h2 {
  text-align: center;
  margin-bottom: 3rem;
  font-size: 2.2rem;
}

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

.project-card {
  background: var(--card-bg);
  border-radius: 12px;
  padding: 1.8rem;
  text-decoration: none;
  color: var(--text);
  transition: all 0.3s ease;
  border: 1px solid var(--border);
}

.project-card:hover {
  transform: translateY(-8px);
  border-color: var(--accent);
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
}

.project-card h3 {
  font-size: 1.4rem;
  margin-bottom: 0.8rem;
}

.project-card p {
  color: #666;
  font-size: 0.95rem;
}

[data-theme="dark"] .project-card p {
  color: #aaa;
}

@media (max-width: 768px) {
  .projects-grid {
    grid-template-columns: 1fr;
  }
}