Environment is shared by every tile on the board — leave on random to roll one value for the whole map, or lock it.

Board size — rows × columns (each tile is 6″). Stored as the first two letters of the code (A=1, D=4, F=6, H=8), so DD… is 4×4 and DF… is 4×6.

Density — how much of each feature the board packs in.