*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}
.container{
    width: 100%;
    min-height:100vh;
    background: linear-gradient(135deg,#153677,#4e085f);
    padding: .75rem;
    overflow-x: hidden;
}
.todo-app{
    width: 30rem;
    background: white;
    margin: 6rem auto;
    padding: 2.75rem 2.25rem;
    border-radius: .75rem;
}
.todo-app h2{
    color: #002765;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.25rem;
}
.todo-app h2 img{
    width: 1.75rem;
    margin-left: .75rem;
}
 .row{
    width: 100%;
    position: relative;
    background: #edeef0;
    border-radius: 1.8rem;
    padding-left: 1.25rem;
    margin-bottom: 1.5rem; 
}
#input-box{
    border: none;
    outline: none;
    background: transparent;
    padding: .75rem .5rem;
    font-size: 1.1rem;
}
.add-btn{
    position: absolute;
    right: 0;
    top: 0;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    border: none;
    outline: none;
    padding: 1rem 1.75rem;
    background: #ff5945;
    color: white;
    font-size: 1.1rem;
    cursor: pointer;
    border-radius: 1.8rem;
}
ul li{
    list-style: none;
    font-size: 1rem;
    padding: .75rem .5rem .75rem 3rem;
    user-select: none;
    cursor: pointer;
    position: relative;
}
/* in mobile screen the checbox is not visible */
ul li::before{
    content: '';
    position: absolute;
    height: 28px;
    width: 28px;
    border-radius: 50%;
    background-image: url('/To-Do List/img/unchecked.png');
    background-size: cover;
    background-position: center;
    top: .55rem;
    left: .5rem;
    border: 1px solid black;
}
ul li.checked{
    color: #555;
    text-decoration: line-through;
}
ul li.checked::before{
    background-image: url('/To-Do List/img/checked.png');
    background-size: cover;
}
ul li span{
    position: absolute;
    right: 0;
    top: .3rem;
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 50%;
    font-size: 1.375rem;
    color: #555;
    line-height: 2.5rem;
    text-align: center;
}
ul li span:hover{
    background: #edeef0;
}
@media (max-width: 640px) {
    .todo-app{
        width: 22rem;
        padding: 1.5rem;
    }
    .row{
        padding-left: .5rem;
    }
    #input-box{
        font-size: 1rem;
        padding: .5rem;
    }
    .add-btn{
        padding: .7rem 1.2rem;
        font-size: 1rem;
    }
}
@media (max-width: 430px) {
    .todo-app{
        width: 18rem;
        padding: 1rem;
    }
    .row{
        padding-left: .75rem;
    }
    #input-box{
        font-size: .9rem;
        padding: .4rem;
    }
    .add-btn{
        padding: .5rem 1rem;
        font-size: .9rem;
    }
}