:root {
  --bg: #ffffff;
  --fg: #1a1a1a;
  --accent: #4f46e5;
  --card-bg: #f5f5f7;
  --border: #e0e0e0;
}

[data-theme="dark"] {
  --bg: #121212;
  --fg: #f0f0f0;
  --accent: #818cf8;
  --card-bg: #1e1e1e;
  --border: #333333;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--fg);
  transition: background 0.2s, color 0.2s;
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  border-bottom: 1px solid var(--border);
}

.logo {
  margin: 0;
  font-size: 1.25rem;
}

.header nav ul {
  display: flex;
  gap: 1.5rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.header nav a {
  color: var(--fg);
  text-decoration: none;
  font-weight: 500;
}

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

#theme-toggle {
  border: none;
  background: var(--card-bg);
  border-radius: 999px;
  width: 2.25rem;
  height: 2.25rem;
  cursor: pointer;
  font-size: 1rem;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

.hero {
  text-align: center;
  padding: 3rem 1rem;
}

.hero h2 {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

button {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 0.6rem 1.4rem;
  border-radius: 8px;
  font-size: 1rem;
  cursor: pointer;
}

button:hover {
  opacity: 0.9;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

#contact-form {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

#contact-form input,
#contact-form textarea {
  padding: 0.6rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--fg);
  font: inherit;
}

footer {
  text-align: center;
  padding: 1.5rem;
  color: #888;
  font-size: 0.875rem;
}