code: public String getLayerProperty(int layerIndex, String propertyName,
  			String def) {
  		Layer layer = (Layer) layers.get(layerIndex);
  		if (layer == null || layer.props == null)
  			return def;
  		return layer.props.getProperty(propertyName, def);
  	}
docs: Get a property given to a particular layer. Note that this method will
  not perform well and should not be used as part of the default code path
  in the game loop.
  
  @param layerIndex
  The index of the layer to retrieve
  @param propertyName
  The name of the property of this layer to retrieve
  @param def
  The default value to return
  @return The value assigned to the property on the layer (or the default
  value if none is supplied)