function menuroll(image,new_image) {
    image.src = new_image;
}

function toggle_layer(layer_name) {
    layer = document.getElementById(layer_name);
    
    if (layer.style.display == 'none') {
        layer.style.display = 'block';
    } else if (layer.style.display == 'block') {
        layer.style.display =  'none';
    }

}