== refill (seeded) ==
start:
OGOGOGOG
RRROGOGO
OGOGOGOG
GOGOGOGO
OGOGOGYG
GOPPPOYO
OGOGOGYG
GOGOGOGO
after clear:
OGOGOGOG
...OGOGO
OGOGOGOG
GOGOGOGO
OGOGOG.G
GO...O.O
OGOGOG.G
GOGOGOGO
after collapse:
.....G.G
OG.GOO.O
OGOOGG.G
GOOGOOOO
OGGOGGGG
GOOGOOOO
OGOGOGGG
GOGOGOGO
after refill:
RROPYGGG
OGRGOOGO
OGOOGGPG
GOOGOOOO
OGGOGGGG
GOOGOOOO
OGOGOGGG
GOGOGOGO
filled 9 holes
ok: refill fills every hole from the seeded stream