mdb-ui-kit/sass/_radios.scss

.form-horizontal .radio {
    margin-bottom: 10px;
}
.radio {
    label {
        cursor: pointer;
        padding-left: 45px;
        position: relative;
        span {
            display: block;
            position: absolute;
            left: 10px;
            top: 2px;
            transition-duration: 0.2s;
        }
        .circle {
            border: 2px solid $lightbg-text;
            height: 15px;
            width: 15px;
            border-radius: 100%;
        }
        .check {
            height: 15px;
            width: 15px;
            border-radius: 100%;
            background-color: $radio-default;
            transform: scale(0);
        }
        .check:after {
            display: block;
            position: absolute;
            content: "";
            background-color: $lightbg-text;
            left: -18px;
            top: -18px;
            height: 50px;
            width: 50px;
            border-radius: 100%;
            z-index: 1;
            opacity: 0;
            margin: 0;
            transform: scale(1.5);
        }
        input[type=radio]:not(:checked) ~ .check:after {
            animation: rippleOff 500ms;
        }
        input[type=radio]:checked ~ .check:after {
            animation: rippleOn 500ms;
        }

    }
    //.variations(#{" input[type=radio]:checked ~ .check"}, background-color, $radio-default);
    //.variations(#{" input[type=radio]:checked ~ .circle"}, border-color, $radio-default);

    input[type=radio][disabled] ~ .check,
    input[type=radio][disabled] ~ .circle {
        opacity: 0.5;
    }

    input[type=radio] { display: none; }
    input[type=radio]:checked ~ .check {
        transform: scale(0.55);
    }
    input[type=radio][disabled] ~ .circle {
        border-color: $lightbg-text;
    }
    input[type=radio][disabled] ~ .check {
        background-color: $lightbg-text;
    }

}

@keyframes rippleOn {
    0% {
        opacity: 0;
    }
    50% {
        opacity: 0.2;
    }
    100% {
        opacity: 0;
    }
}

@keyframes rippleOff {
    0% {
        opacity: 0;
    }
    50% {
        opacity: 0.2;
    }
    100% {
        opacity: 0;
    }
}