How about something really simply: Give asteroids proper physics. By this I mean make them bounce away (with proper spin and velocity) when they collide. Also, give each asteroid some amount of ''health'', and each time two asteroids collide they lose some health (how much depending on the speed of impact and the size of the two asteroids, bigger ones lose less health when hit by smaller ones and smaller ones lose more health when hit by larger ones). When the health is 0, it blows up as if it were shot (as long as it is a large enough size to split - it won''t just dissapear if its the smallest size).

never forget about gameplay, ask yourself how an idea impact the play style and the gameplay, it''s not about endless possibility but fun gameplay

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be good
be evil
but do it WELL
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