body {
    font-family: sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f2f5;
    margin: 0;
}

.container {
    background-color: #fff;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    width: 100%;
    max-width: 400px;
}

h1 {
    text-align: center;
    color: #333;
}

.input-area {
    display: flex;
    margin-bottom: 20px;
}

#todo-input {
    flex-grow: 1;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
    margin-right: 10px;
}

#add-button {
    padding: 10px 15px;
    border: none;
    background-color: #007bff;
    color: #fff;
    border-radius: 4px;
    cursor: pointer;
}

#add-button:hover {
    background-color: #0056b3;
}

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

#todo-list li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: #f9f9f9;
    padding: 10px;
    border: 1px solid #eee;
    border-radius: 4px;
    margin-bottom: 10px;
}

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

#todo-list li span {
    flex-grow: 1;
    cursor: pointer;
}

#todo-list li button {
    margin-left: 10px;
    padding: 5px 10px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    color: #fff;
}

#todo-list li .delete-button {
    background-color: #dc3545;
}

#todo-list li .delete-button:hover {
    background-color: #c82333;
}

.back-button {
    display: block;
    margin-top: 20px;
    padding: 10px 15px;
    background-color: #6c757d;
    color: #fff;
    text-align: center;
    text-decoration: none;
    border-radius: 4px;
    max-width: 150px;
    margin-left: auto;
    margin-right: auto;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.back-button:hover {
    background-color: #5a6268;
}