* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, Helvetica, sans-serif;
}

body {
    min-height: 100vh;
    background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
    display: flex;
    justify-content: center;
    align-items: center;
    color: #fff;
}

.container {
    background: #1e293b;
    padding: 25px;
    width: 100%;
    max-width: 420px;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.4);
}

h1 {
    text-align: center;
    margin-bottom: 20px;
    color: #38bdf8;
}

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

#todo-input {
    flex: 1;
    padding: 10px 12px;
    border: none;
    border-radius: 6px;
    outline: none;
    font-size: 15px;
}

#add-btn {
    padding: 10px 16px;
    border: none;
    border-radius: 6px;
    background: #38bdf8;
    color: #0f172a;
    font-weight: bold;
    cursor: pointer;
    transition: 0.3s;
}

#add-btn:hover {
    background: #0ea5e9;
}

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

#todo-list li {
    background: #334155;
    padding: 10px;
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 10px;
}

#todo-list li span {
    flex: 1;
    margin-left: 8px;
    word-break: break-word;
    cursor: pointer;
}

#todo-list li button {
    background: #ef4444;
    border: none;
    padding: 6px 10px;
    border-radius: 4px;
    color: #fff;
    cursor: pointer;
    transition: 0.3s;
}

#todo-list li button:hover {
    background: #dc2626;
}

#todo-list input[type="checkbox"] {
    cursor: pointer;
    accent-color: #38bdf8;
}

/* Mobile responsive */
@media (max-width: 480px) {
    .container {
        padding: 18px;
    }

    h1 {
        font-size: 22px;
    }
}