css/style.css

div.row-widget.stRadio > div {
 flex-direction: row;
 align-items: stretch;
}

div.row-widget.stRadio > div[role="radiogroup"] > label[data-baseweb="radio"]  {
    /*background-color: rgb(240, 242, 246);*/
    padding-right: 10px;
    /*padding-left: 4px;*/
    padding-bottom: 3px;
    margin: 4px 0px;
    border-radius: 0;
    border-bottom: 2px solid rgba(169, 169, 169, 0.3);
    transition: border-bottom-color 0.2s ease 0s;
}

/*change the background color of the parent label of the selected radio button*/
div.row-widget.stRadio > div[role="radiogroup"] > label[data-baseweb="radio"]:has( > input[type="radio"]:checked) {
    /*background-color: blanchedalmond;*/
    border-bottom: 2px solid red;
    transition: border-bottom-color 0.2s ease 0s;
}

/*hide the circle of the radio button*/
div.row-widget.stRadio > div[role="radiogroup"] > label[data-baseweb="radio"] > div:first-child {
    display: none;
}