function hideLevel(_levelId) {
    var thisLevel = document.getElementById(_levelId);
    thisLevel.style.display = "none";
    var thisLevelButton = document.getElementById(_levelId + "Bt");

    thisLevelButton.className = "inactive";
}

function initialHiding() {
    hideLevel("pol2");
    hideLevel("pol3");
    hideLevel("pol4");
}

function showLevel(_levelId, _slevelId, _tlevelId, _flevelId) {
    var thisLevel = document.getElementById(_levelId);
    var thisLevelButton = document.getElementById(_levelId+"Bt");
    
    thisLevelButton.className = "active";
    thisLevel.style.display = "block";
    
    hideLevel(_slevelId);
    hideLevel(_tlevelId);
    hideLevel(_flevelId);
}