radio button css

HTML

<h3>Radio Buttons</h3>

<label>
    <input type='radio' name="radio_group_1" value="option_1" />
</label>
<input type='radio' name="radio_group_1" value="option_2" checked='checked' />

CSS

input[type='radio'] {
    width: 20px;
    line-height: 20px;
    text-align: center;
}
input[type='radio']:before {
    opacity: 1;
    content: ' ';
    display: inline-block;
    width: 20px;
    height: 20px;
    border: solid 1px blue;
    border-radius: 10px;
    background-color: white;
}
input[type='radio']:checked:before {
    background-color: red;
}
input[type='radio']:disabled:before {
    background-color: #ededed;
}