Now, we add the small circle inside when this input is checked. We will utilize the CSS3 :checked pseudo-class along with the Bullet HTML character (•). This bullet will be delivered through content property, thus we need to convert this HTML character for CSS with a Entity Conversion Tool.

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input[type=radio]:checked + label:before {  
    content: "\2022";  
    color: #f3f3f3;  
    font-size: 30px;  
    text-align: center;  
    line-height: 18px;  
} 
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