input[type=checkbox]{
cursor: pointer;
position: relative;
width: 15px;
height: 15px;
font-size: 14px;
}

input[type=checkbox]::after{
position: absolute;
top: 0;
background-color: red;
color: #000;
width: 15px;
height: 15px;
display: inline-block;
visibility: visible;
padding-left: 0px;
text-align: center;
content: ' ';
border-radius: 3px
}

input[type=checkbox]:checked::after{
content: "✓";
font-size: 12px;
font-weight: bold;
}