private void UnPaintTile( MapLayer layer, Vector2 position )
{
layer.SetTile( position, -1 );
}
private void PaintTile( MapLayer layer, Vector2 position )
{
if( !_layerTileMap.ContainsKey( layer ) )
_layerTileMap.Add( layer, 0 ); // the first tile is the default
layer.SetTile( position, _layerTileMap[ layer ] );
}