Here are some really small GUI program using C with windows API.
Binary: frac.exe (1K)
Source code: frac.c
Rules: each time click a piece adjacent to the yellow one to perform an exchange until the original desktop is recovered.
Binary: scramble.exe (4K)
Source code: scramble.c.

Two snapshots: the initial scrambled desktop (left) and final unscrambled one (right):