body {
    background-color: #f3f4f6;
    font-family: 'Segoe UI', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.back-btn {
    position: fixed;
    top: 20px;
    left: 20px;
    padding: 10px 18px;
    background: #6c5ce7;
    color: white;
    text-decoration: none;
    border-radius: 8px;
    font-weight: 500;
    font-size: 0.9rem;
    transition: background 0.2s, transform 0.2s;
    z-index: 1000;
}
.back-btn:hover { background: #5a4ad1; transform: translateX(-3px); }

.todo-card {
    background: white;
    width: 350px;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.1);
}

h2 { margin-top: 0; color: #333; }

.input-row {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

input {
    flex: 1;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
    outline: none;
}

button {
    padding: 10px 20px;
    background: #6c5ce7;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: bold;
}
button:hover { background: #5a4ad1; }

.secondary {
    background: #e74c3c;
    width: 100%;
    margin-top: 20px;
}

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

li {
    background: #f9f9f9;
    padding: 10px;
    border-bottom: 1px solid #eee;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
}

li:hover { background: #f0f0f0; }

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