A more advanced tile engine

In Robot Rampage, we built a simple tile engine that displayed a single layer of tiles from a two-dimensional array of integers, which represented the tiles associated with each map square. For Gemstone Hunter, we will construct a new tile engine that handles multiple tile layers, including a layer of tiles that are drawn in the foreground, appearing in front of the player:

Since we need to store more information about an individual map square, we will begin by defining a class that will contain all of the information we need about a particular square.