Improved level generation

[walsh9]

Possibilities

• Place impassable walls during generation.
• Sometimes, use symmetry to create pretty levels.
• Sometimes, place prefab terrain shapes.

[walsh9]

• Digger that creates crissy-crossy levels like #.
• Digger that creates branchier tunnels that don't turn in on themselves as much.
• Energy placer that places rectangles instead of puddles.

[walsh9]

• [? ] Prevent impossible layouts (Maybe just don't place crates near walls)
• Add impassible obstacles
• Add destructible obstacles
• Add alternate digger patterns