There is - to the standard Quake .map format Neverball uses.
Score: 7
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However, I think that you do not need 'time' based variables in the form of reachable(x,y,t) = reachable(nx,ny,t-1)
Enforcing connectivity through single-commodity flows is IMO better to enforce flood fill (also introduces additional variables but is typically easier to solve with CP heuristics): Score: 2
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Cool puzzle!
see seppe.net and blog.macuyiko.com