*{
    margin: 0;
    padding: 0;
    font-family: 'poppins',sans-serif;
    box-sizing: border-box;
}
.container{
    width: 100%;
    min-height: 100vh;
    background: linear-gradient(135deg,#153677,#4e085f);
    padding: 10px;
}
.todo-app{
    width: 100%;
    max-width: 540px;
    background: #fff;
    margin: 100px auto 20px;
    padding: 40px 30px 70px;
    border-radius: 10px;
}
.todo-app h1{
    display: flex;
    justify-content: center;
    align-items: center;
    margin-bottom: 20px;
}

.row{
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #edeef0;
    border-radius: 30px;
    padding-left: 20px;
    margin-bottom: 25px;
}
input{
    flex: 1;
    border: none;
    outline: none;
    background: transparent;
    padding: 10px;
    font-weight: 14px;
}
button{
    border: none;
    outline: none;
    padding: 16px 50px;
    background: #ff5945;
    color: #fff;
    font-size: 16px;
    cursor: pointer;
    border-radius: 40px;
}
ul li{
    list-style: none;
    font-size: 17px;
    padding: 12px 8px 12px 50px;
    user-select: none;
    cursor: pointer;
    position: relative;
}

ul li::before{
    content: '';
    position: absolute;
    height: 28px;
    width: 28px;
    border-radius: 50%;
    background-image: url(images/uncheck-mark-sign.png);
    background-size: cover;
    background-position: center;
    top: 8px;
    left: 8px;
}

ul li.checked{
    color: #555;
    text-decoration: line-through;
}

ul li.checked::before{
    background-image: url(images/check-mark-sign.png);
}

ul li span{
    position: absolute;
    right: 0;
    top: 5px;
    width: 40px;
    height: 40px;
    font-size: 22px;
    color: #2681e2;
    line-height: 40px;
    text-align:center;
    border-radius: 50%;
}

ul li span:hover{
    background: #edeef0;
}


/* For Tablets (max-width: 768px) */
@media (max-width: 768px) {
    .todo-app {
        width: 90%;
        margin: 50px auto;
        padding: 30px 20px 60px;
    }

    button {
        padding: 14px 30px;
        font-size: 14px;
    }

    input {
        padding: 8px;
        font-size: 14px;
    }

    ul li {
        font-size: 15px;
        padding: 10px 8px 10px 45px;
    }
}

/* For Mobile Devices (max-width: 480px) */
@media (max-width: 480px) {
    .todo-app {
        width: 95%;
        margin: 30px auto;
        padding: 20px 15px 50px;
    }

    h1 {
        font-size: 22px;
    }

    .row {
        flex-direction: column;
        align-items: stretch;
        gap: 10px;
        padding-left: 10px;
    }

    input {
        width: 100%;
        padding: 10px;
        font-size: 14px;
    }

    button {
        position: absolute;
        left: 68%;
        width: 100px;
        padding: 10px;
        font-size: 14px;
        border-radius: 40px;
    }

    ul li {
        margin-top: 10px;
        font-size: 14px;
        padding: 14px 6px 10px 40px;
    }

    ul li span {
        font-size: 18px;
        right: 5px;
        top: 5px;
    }
}