* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Arial, Helvetica, sans-serif;
    background-color: #0f172a;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    color: white;
}

.container {
    background-color: #1e293b;
    padding: 30px;
    border-radius: 15px;
    width: 400px;
    box-shadow: 0 0 20px; 
}

h1 {
    text-align: center;
    margin-bottom: 20px;
}

.input-section {
    display: flex;
    gap: 10px;
}

input {
    flex: 1;
    padding: 12px;
    border: none;
    border-radius: 8px;
    outline: none;
    font-size: 1rem;
}

button {
    padding: 12px 18px;
    border: none;
    border-radius: 8px;
    background-color: #38bdf8;
    color: white;
    cursor: pointer;
    transition: 0.3s;
}

button:hover {
    background-color: #0284c7;
}

ul {
    margin-top: 25px;
    list-style: none;
}

li {
    background-color: #334155;
    padding: 12px;
    border-radius: 8px;
    margin: 10px;

    display: flex;
    justify-content: space-between;
    align-items: center;
}

.completed {
    text-decoration: line-through;
    opacity: 0.6;
}

/* RESPONSIVE DESIGN */
@media (max-width: 600px){
    .container{
        width: 90%;
        padding: 20px;
    }

    h1 {
        font-size: 28px;
    }

    .input-section{
        flex-direction: column;
        gap: 10px;
    }

    #taskInput{
        width: 100%;
    }

    #addBtn{
        width: 100%;
    }

    li{
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    li button {
        width: 100%;
    }
}