Layouts are up to 5 layers tall. Each layer is a grid of 16x8 tiles.

Tile size (faces) is 30x40 px, but the layouts subdivide it into
2x2 quarters of 15x20 px each. That way we can have tiles placed in
intermediate positions respect to each other.

To handle this, only the first quarter in the tilemap (i.e. the tile's
top-left part) is used when reading the maps, and the other 3 quarters
are secondary.


Also, when drawn, there are extra features not drawn in the tile map:
tile edges and shadows. This also causes each layer to be slightly
displaced respect to the layer below.
