style.css

*{
    margin: 0%;
    padding: 0%;
    box-sizing: border-box;
}
.container{
    width: 100%;
    min-height: 100vh;
    background: linear-gradient(120deg, rgb(146, 209, 228),rgb(42, 114, 192));
    padding:10px ;
}
.todo-app{
    width: 100%;
    max-width: 540px;
    background: #ffffff;
    margin: 100px auto 20px;
    padding: 40px 30px 70px;
    border-radius: 10px;
}
.todo-app h2{
color:rgb(14, 14, 84) ;
display: flex;
align-items: center;
margin-bottom: 20px;
}
.todo-app h2 img{
    width: 30px;
    margin-left: 20px;
}
.row{
    display: flex;
    align-items: center;
    justify-content: space-between;
    background-color:#d2dde7 ;
    border-radius: 20px;
    padding-left: 20px;
    margin-bottom: 20px;
}
input{
    /* will take the full width */
    flex: 1;
    border: none;
    outline: none;
    background: transparent;
    padding: 10px;
}
button{
    border: none;
    outline: none;
    padding: 10px 20px;
    background-color: rgb(241, 112, 37);
    border-radius: 15px;
    color: #ffffff;
    cursor: pointer;
}
ul li{
    list-style: none;
    font-size: 20px;
    padding: 12px 8px 12px 50px;
    user-select: none;
    cursor: pointer;
    position: relative;
}
/* adding pseudo element  for unchecked*/
ul li::before{
    content: "";
    position: absolute;
    height: 28px;
    width: 28px;
    border-radius: 50%;
    background-image: url(./images/unchecked.png);
    background-size: cover;
    background-position: center;
    top: 8px;
    left: 8px;
}
/*checked tasks */
ul li.checked{
    color: #808080;
    text-decoration:line-through;
}
ul li.checked::before{
    background-image: url(./images/checked.png);
}
ul li span{
    position: absolute;
    right: 0;
    top: 8px;
     width: 30px;
    height: 30px;
    font-size: 22px;
    color: #808080c1;
    line-height: 30px;
    text-align: center;
    border-radius: 50%;
}
ul li span:hover{
    background-color: #d2dde7;
}