:root {
  --bg-color: #f4f6f8;
  --card-bg: #ffffff;
  --text-color: #333333;
  --primary-color: #4f46e5;
}

[data-theme="dark"] {
  --bg-color: #0f172a;
  --card-bg: #1e293b;
  --text-color: #f8fafc;
  --primary-color: #6366f1;
}

body {
  font-family: system-ui, -apple-system, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  margin: 0;
  padding: 20px;
}

.container { 
  max-width: 900px; 
  margin: 0 auto; 
}

.card { 
  background: var(--card-bg); 
  padding: 20px; 
  border-radius: 12px; 
  margin-bottom: 20px; 
  box-shadow: 0 2px 8px rgba(0,0,0,0.05); 
}

.greeting-card { 
  text-align: center; 
}

.grid-layout { 
  display: grid; 
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); 
  gap: 20px; 
}

.timer { 
  font-size: 2.5rem; 
  font-weight: bold; 
  margin: 15px 0; 
  text-align: center; 
}

.button-group, form { 
  display: flex; 
  gap: 10px; 
  margin-bottom: 15px; 
}

input { 
  flex: 1; 
  padding: 8px 12px; 
  border: 1px solid #ccc; 
  border-radius: 6px; 
}

button { 
  background: var(--primary-color); 
  color: white; 
  border: none; 
  padding: 8px 16px; 
  border-radius: 6px; 
  cursor: pointer; 
}

ul { 
  list-style: none; 
  padding: 0; 
}

li { 
  display: flex; 
  justify-content: space-between; 
  padding: 8px 0; 
  border-bottom: 1px solid #eee; 
}

.done { 
  text-decoration: line-through; 
  opacity: 0.6; 
}

.links-grid { 
  display: flex; 
  flex-wrap: wrap; 
  gap: 10px; 
}

.theme-toggle { 
  position: fixed; 
  bottom: 20px; 
  right: 20px; 
}