.checkbox-round {
    width: 1.3em;
    height: 1.3em;
    background-color: white;
    border-radius: 50%;
    vertical-align: middle;
    border: 1px solid #ddd;
    -webkit-appearance: none;
    outline: none;
    cursor: pointer;
}

.checkbox-round:checked {
    background-color: green;
    background-image:  url('images/checkbox.png') , linear-gradient(to bottom, #3DC979 , #4DB7B3);
    background-repeat: no-repeat;
    background-position: center ;
}