SDLlopan OS4:
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quick and dirty port.
Ported on request from cobra.

Within the game, 
<ESCAPE> exits, and 
<RETURN> reshuffles the board.
The arrow keys work as undo/redo.

F1 switches the tilesets, the data/tiles#.pcx files are used.
F2 switched the background, the data/bg#.pcx files are used.
In both cases, number files from 0.

To save disk space you can delete the data/bg*.pcx files you don't want,
then renumber them starting from 0.