style.css

* {
    margin: 0px;
    padding: 0px;
    box-sizing: border-box;
    font-family: 'Ubuntu', sans-serif;
}

main {
    background-color: #6a89cc;
    height: 100vh;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    

}
.box {
    width: 700px;
    min-height: 500px;
    background-color: white;
    border-radius: 5px;
    padding: 10px;

}

#item {
    width: 100%;
    padding: 5px;

}

#item {
    padding: 10px;
    font-size: 15px;
    font-weight: bold;
    display: block;
    border: none;
    outline:none;
    box-shadow: 0px 0px 2px gray;

}

#to-do-box {
    list-style: none;
    margin-top: 10px;

}

#to-do-box  li {

    padding: 10px;
    color: white;
    background-color:#576574;
    position: relative;
    margin-top: 5px;
    
    
    
}

#to-do-box  li i {
    position: absolute;
    right: 10px;
    top: 10px;
}

#tick
{
    text-decoration: line-through;
    margin-left: 15px;
    
}

.completed {
    text-decoration: line-through;
}
.done {
    text-decoration: line-through;
    color: black;
    background-color: yellow !important;
}