:root {
  --bg-color: whitesmoke;
  --text-color: #222;
  --card-bg: whitesmoke;
  --card-border: gray;
  --accent: #0077ff;
  --shadow: rgba(0, 0, 0, 0.1);
}

[data-theme='dark'] {
  --bg-color: #121212;
  --text-color: #f1f1f1;
  --card-bg: #1e1e1e;
  --card-border: #333;
  --accent: #4da6ff;
  --shadow: rgba(0, 0, 0, 0.6);
}

body {
  margin: 0;
  font-family: system-ui, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
}

a.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--accent);
  color: #fff;
  padding: 0.5rem;
  z-index: 100;
  transition: top 0.3s;
}
a.skip-link:focus {
  top: 0;
}

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

header h1 {
  margin: 0;
  font-size: 1.5rem;
}

button#theme-toggle {
  background: var(--accent);
  color: #fff;
  border: none;
  padding: 0.5rem 1rem;
  border-radius: 5px;
  cursor: pointer;
  transition: background 0.3s;
}
button#theme-toggle:hover {
  background: #005fcc;
}

main {
  padding: 2rem;
  max-width: 1200px;
  margin: auto;
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
}

.project-card {
  display: block;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 10px;
  padding: 2rem;
  text-align: center;
  text-decoration: none;
  color: var(--text-color);
  font-weight: bold;
  box-shadow: 0 4px 8px var(--shadow);
  transition:
    transform 0.3s,
    box-shadow 0.3s;
  position: relative;
  overflow: hidden;
}

.project-card::after {
  content: '';
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: linear-gradient(
    120deg,
    rgba(255, 255, 255, 0.2),
    transparent 60%
  );
  transform: rotate(25deg);
  transition: transform 0.6s;
}

.project-card:hover {
  transform: translateY(-5px) scale(1.03);
  box-shadow: 0 8px 16px var(--shadow);
  background-color: darkgray;
}

footer {
  text-align: center;
  padding: 1rem;
  border-top: 1px solid var(--card-border);
  margin-top: 2rem;
}