body {
  margin: 0;
  font-family: Arial, sans-serif;
  line-height: 1.5;
  color: #333;
  background: #f5f5f5;
}

header {
  padding: 20px;
  text-align: center;
  color: #fff;
  background: #2c3e50;
}

header h1 {
  margin: 0 0 10px;
}

nav a {
  margin: 0 10px;
  color: #fff;
}

main {
  max-width: 700px;
  margin: 0 auto;
  padding: 20px;
}

section {
  margin-bottom: 20px;
  padding: 20px;
  background: #fff;
  border: 1px solid #ddd;
  border-radius: 4px;
}

h2 {
  margin-top: 0;
}

button {
  padding: 8px 14px;
  cursor: pointer;
}

input {
  padding: 8px;
}

ul {
  padding-left: 20px;
}

li {
  margin-top: 6px;
  cursor: pointer;
}

li.done {
  color: #999;
  text-decoration: line-through;
}

footer {
  padding: 15px;
  text-align: center;
  color: #666;
}