function showLevel(_levelId) {
    var thisLevel = document.getElementById(_levelId);
    thisLevel.style.display = "block";
}
function hideLevel(_levelId) {
    var thisLevel = document.getElementById(_levelId);
    if (thisLevel != null) {
        thisLevel.style.display = "none";
    }
}
function toggleLevel(_levelId) {
    var thisLevel = document.getElementById(_levelId);
    if (thisLevel.style.display == "none") {
        thisLevel.style.display = "block";
    } else {
        thisLevel.style.display = "none";
    }
}