style.css

body{background-color: #34495e;}

#container{
    widows: 350px;
    width:400px;
    height: auto;
    margin: auto;
    text-align: center;
    background: white;
    height: 780px;
    overflow: auto;
    color: black;
    border: 10px solid #01a3a4;
    border-radius:10px;
}

h1{ 
    margin-top:50px;
    margin-bottom: 50px;
    text-transform: uppercase;
    text-align: center;
}

#container ul{
    margin-top:50px;
    padding-left: 0;
}

#container ul li{
    list-style:none;
    border:2px solid #b5c5dd;
    width: 80%;
    transition: opacity 0.5s ease-in-out;
    height: 40px;
    margin: 10px auto;
    text-align: left;
}

#container ul li label{
    margin: 0 auto;
    vertical-align: middle;
    height: 100px;
    line-height: 40px;
    font-size: 18px;
}

#container ul li #check{
    float: left;
    width: 30px;
    height: 30px;
    margin: 5px;
    -webkit-appearance: none;
    border: 2px solid #b5c5dd;
    position: relative;
    outline: 0;
}

#container ul li #check:checked:after{
    content:'\2714';
    font-size: 20px;
    position: absolute;
    top: 0px;
    left: 7px;
    color: black;
}

#container ul li input[type="checkbox"]:checked+label{
    text-decoration: line-through;
    color: rgba(0,0,0,.3);
}

#container .controls {
    width:60%;
    margin: 0 auto;
}

#container  .controls  #input {
width:100%;
height: 30px;
font-size: 20px;
padding-left:5px;
box-sizing: border-box;
margin-bottom: 20px;
border: 2px solid #b5c5dd;
border-radius:10px;
}

#container .controls #input:focus{
    outline:0;
}

#container .controls button{
    width:100%;
    background: white;
    border: none;
    height: 35px;
    margin-top: 10px;
    cursor: pointer;
    color: white;
}

#container .controls button:focus{
    outline: 0px;
}

#container .controls button:hover{
    transform: scale(1.09);
}

#container .controls #add{
    background-color:  #2980b9;
    border-radius:10px;
}

#container .controls #remove{
    background-color:  #b929b2;
    border-radius:10px;
}

#container .mycheck{
    opacity:1px;
    border-radius:10px;
}

.visual{
    opacity:1 !important;
    border-radius:10px;
}