style.css

*{
    margin: 0;
    padding: 0;
    font-family: 'poppins',sans-serif;
    box-sizing: border-box;
}
.container{
    width: 100%;
    min-height: 100vh;
    background: linear-gradient(140deg, rgb(33, 5, 192),#db11dbd8);
    /* background-color: #2ec194; */
    padding: 10px;    
}
.todo-app{
    width: 100%;
    max-width: 540px;
    background: #ffff;
     border-radius: 15px;
     box-shadow: -4px -4px 4px rgba(50, 4, 219, 0.6),
                 4px 4px 4px rgba(187, 2, 224, 0.904),
                inset -2px -2px  2px rgba(207, 3, 248, 0.6),
              inset 2px  2px  2px rgba(49, 2, 219, 0.9);
    margin: 100px auto 20px;
    padding: 40px 30px 70px;
}
.todo-app h2{
    color: #130065;
    display: flex;
    align-items: center;
    margin-bottom: 20px;
}
.todo-app h2 img{
    width: 35px;
    margin-left: 10px;
}
.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: #cf28d4;
    box-shadow: -15px -15px 15px rgba(255, 255, 255, 0.2),
                 15px 15px 15px rgba(0, 0, 0, 0.1),
                inset -5px -5px  5px rgba(255, 255, 255, 0.2),
              inset 5px  5px  5px rgba(0, 0, 0, 0.1);
    color: #fff;
    font-size: 16px;
    cursor: pointer;
    border-radius: 40px;
    }
ul li{
    list-style: none;
    font-size: 17px;
    padding: 12px 8px 12px 15px;
    margin-left: 15px;
    user-select: none;
    cursor: pointer;
    position: relative;
}
ul li::before{
    content: '';
    position: absolute;
    height: 30px;
    width: 30px;
    border-radius: 50%;
    background-image: url(icon-circle.png);
    background-size: cover;
    background-position: center;
    top: 7px;      
    left:-22px;
}
ul li.checked{
    color: #555;
    text-decoration: line-through;
}
ul li.checked::before{
    background-image: url(check.png);
}
ul li span{
    position: absolute;
    right: 0;
    top: 5px;
    width: 40px;
    height: 40px;
    font-size: 22px;
    color: #555;
    line-height: 40px;
    text-align: center;
    border-radius:50% ;
}
ul li span:hover{
    background: #edeef0;
}