style.css

*{
    padding: 0px;
    margin: 0px;
    font-family: sans-serif;
    box-sizing: border-box;
}
.container
{
    background: linear-gradient(135deg,#153677,#4e0854);
    width: 100%;
    height: 100vh;
    padding: 10px;
}
.todoapp{
    margin: 100px auto 0px;
    width: 100%;
    max-width: 574px;
    background-color: #fff;
    border-radius: 10px;
    padding: 40px 30px 70px;
    font-family: 'Franklin Gothic Medium', 'Arial Narrow', Arial, sans-serif;
}
.todoapp h2{
    display: flex;
    align-items: center;
}
.todoapp img{
    height: 30px;
    margin-left: 10px;
}
.row
{
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #edeef0;
    border-radius: 30px;
    padding-left: 10px;
    margin-bottom:  10px;

}
input
{
    border: none;
    padding: none;
    flex:1;
    background:transparent;
    padding: 10px;
    margin-top: 7px;
}
button{
    border: none;
    padding:16px 50px;
    outline: none;
   border-radius: 30px;
   background-color: red;
   font-size:16px;
   
}
ul li{
    list-style: none;
    padding: 15px 10px 10px 15px;
    margin: 0px 15px;
    font-size: 17px;
    user-select: none;
    cursor: pointer;
    position: relative;
    justify-content: space-between;
}
ul li.checked
{
    color:#555f;
    text-decoration: line-through;
    
}
ul li.checked::before{
    background:url(images/checked.png);
    
}
ul li::before
{
    content: "";
    border-radius: 50%;
    background-image: url(images/unchecked.png);
    height: 28px;
    width:28px;
    position:absolute;
    background-size: cover;
    background-position: center;
    margin-left: -36px;
    align-items: center;
    margin-top: -4px;
}
ul li span{
    position: absolute;
    top: 5px;
    right: 0; /*will push the button to extreme right*/
    width: 40px;
    height: 40px;
    text-align: center;
    line-height: 40px;
   font-size: 22px;
   color: #555; 
   border-radius: 50%;
}
ul li span:hover{
    background: #4e0854;
    cursor: pointer;
}