var checkedGroups = 0;

function monitorRadio() {
    document.querySelectorAll('input[type="radio"]').forEach(function (el) {
        el.addEventListener('change', incCounter, { once: true });
    });
}

function incCounter() {
    checkedGroups++;
}

function checkCount() {
    if (checkedGroups === 5) {
        countdown();
    }
}

window.addEventListener("keydown", function (event) {
    if (event.defaultPrevented) {
        return;
    }

    checkCount();

    switch (event.key) {
        case "a":
            checkedGroups++;
            getid = 'a'+checkedGroups;
            document.getElementById(getid).checked = true;
            checkCount();
            break;
        case "b":
            checkedGroups++;
            getid = 'b'+checkedGroups;
            document.getElementById(getid).checked = true;
            checkCount();
            break;
        default:
            checkCount();
            return;
    }

    event.preventDefault();
}, true);