body {
  font-family: Arial, sans-serif;
  background: #f5f5f5;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  margin: 0;
  padding: 1rem;
}

.todo-container {
  background: #fff;
  padding: 1.5rem;
  border-radius: 8px;
  width: 100%;
  max-width: 400px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
}

h2 {
  margin: 0 0 1rem;
  font-size: 1.4rem;
  text-align: center;
}

input {
  width: 100%;
  padding: 0.75rem;
  margin-bottom: 0.75rem;
  border: 1px solid #ddd;
  border-radius: 4px;
  outline: none;
  font-size: 1rem;
}

button {
  width: 100%;
  padding: 0.75rem;
  margin-bottom: 0.5rem;
  border: none;
  border-radius: 4px;
  background: #333;
  color: white;
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.3s;
}

button:hover {
  background: #555;
}

ul {
  list-style: none;
  padding: 0;
  margin: 1rem 0 0;
}

li {
  padding: 0.75rem;
  margin-bottom: 0.5rem;
  border: 1px solid #ddd;
  border-radius: 4px;
  cursor: pointer;
  word-wrap: break-word;
}

li:hover {
  background: #f0f0f0;
}

li.completed {
  text-decoration: line-through;
  color: #888;
}

@media (max-width: 500px) {
  h2 {
    font-size: 1.2rem;
  }

  input, button, li {
    font-size: 0.9rem;
    padding: 0.6rem;
  }
}