style.css

html {
    font-size: 100%;
    font-family: sans-serif;
}

#parameter {
    vertical-align: middle;
}

input[type=radio] {
    margin-right: 8px;
}

input[type=radio] {
    display: none;
}

input[type=radio] + label {
    position: relative;
    padding: 0 15px 0 20px;
    font-size: medium;
}

input[type=radio] + label::before {
    position: absolute;
    content: '';
    display: block;
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: #fff;
    border: 1px solid #d2d2d2;
    left: 0;
    top: 0;
}

input[type=radio] + label::after {
    position: absolute;
    content: '';
    display: block;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: #666666;
    left: 4px;
    top: 4px;
    opacity: 0;
}

input[type=radio]:checked + label::before {
    border: 1px solid #666666;
}

input[type=radio]:checked + label::after {
    opacity: 1;
}