Here's custom CSS to handle checkboxes and radios styled as buttons:

Start your code here/* begin checkbox and radio button style overrides */
.frm_display_format_buttons .frm_label_button_container {
	border-radius: 30px !important;
	border: 1px solid #4199fd !important;
}
.with_frm_style .frm_label_button_container:hover {
	border: 1px solid rgba(255,255,255,0.0) !important;
}
.frm_display_format_buttons .frm_label_button_container {
    -webkit-transition: opacity .45s cubic-bezier(.25,1,.33,1),transform .45s cubic-bezier(.25,1,.33,1),border-color .45s cubic-bezier(.25,1,.33,1),color .45s cubic-bezier(.25,1,.33,1),background-color .45s cubic-bezier(.25,1,.33,1);
    transition: opacity .45s cubic-bezier(.25,1,.33,1),transform .45s cubic-bezier(.25,1,.33,1),border-color .45s cubic-bezier(.25,1,.33,1),color .45s cubic-bezier(.25,1,.33,1),background-color .45s cubic-bezier(.25,1,.33,1);
}
.frm_display_format_buttons .frm_label_button_container:hover {
    border-color: #0066cc !important;
	background-color: #0066cc !important;
	color: #fff;
}
.frm_display_format_buttons input[type="radio"]:focus + .frm_label_button_container, 
.frm_display_format_buttons input[type="checkbox"]:focus + .frm_label_button_container, 
.frm_nps__button:hover, .frm_nps__button:focus {
    border-color: #0066cc !important;
	background-color: #0066cc !important;
	color: #fff;
}
.frm_display_format_buttons input[type="radio"]:checked + .frm_label_button_container, 
.frm_display_format_buttons input[type="checkbox"]:checked + .frm_label_button_container {
    border-color: #0066cc !important;
	background-color: #0066cc !important;
	color: #fff;
}
/* end checkbox and radio button style overrides */