* {
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: #f5f5f5;
    margin: 0;
    padding: 20px;
}

.container {
    max-width: 500px;
    margin: 0 auto;
    background: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

h1 {
    margin-top: 0;
    color: #333;
}

form {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

input[type="text"] {
    flex: 1;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 16px;
}

input[type="text"]:focus {
    outline: none;
    border-color: #007bff;
}

button {
    padding: 10px 20px;
    background: #007bff;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 16px;
}

button:hover {
    background: #0056b3;
}

#todo-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

#todo-list li {
    display: flex;
    align-items: center;
    padding: 10px;
    border-bottom: 1px solid #eee;
    gap: 10px;
}

#todo-list li:last-child {
    border-bottom: none;
}

#todo-list li.completed .todo-title {
    text-decoration: line-through;
    color: #999;
}

.todo-title {
    flex: 1;
}

.delete-btn {
    background: #dc3545;
    padding: 5px 10px;
    font-size: 18px;
    line-height: 1;
}

.delete-btn:hover {
    background: #c82333;
}

input[type="checkbox"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
}