WASD to move, G to open map grid list, and B to close it. I would highly suggest playing on a low resolution, or out of Fullscreen mode so you don't see as big gaps between blocks.
There is a list inside the Layer1 code, change the contents in the add [Blank] to list blocks. for example: G(for grass) _(for nothing) C(for cobblestone) S(for stone) P(for path block) and D(for dirt) in a pattern like: GGGGGGGGG SSSSSSSSSS PPPPPPPPPP CCCCCCCCC DDDDDDDDD for a different block in each layer. Each pattern is flipped, so instead of seeing the pattern: GGGGGGGGG SSSSSSSSSS PPPPPPPPPP CCCCCCCCC DDDDDDDDD you see: DDDDDDDDD CCCCCCCCC PPPPPPPPPP SSSSSSSSSS GGGGGGGGG. Don't worry I'll make an external map editor to make this process easier but for now this is just a test.