Just played the game, no crashes, and had quite a bit of fun. Cool idea!
I never managed to actually make any of the levels correctly in the level building section and was wondering... do I only get a point bonus for making the level perfectly? Or do I get a point bonus on each tile that is placed in the correct space? I couldn't quite figure it out. If it's the former, that seems a bit harsh, though I could be sore from being a tile or two off on a few levels.
No, the way it works is you get 1000 points if you match a tile correctly, or 10 points if you don't. Then there's an extra 10000 points at the end of the level if you matched every tile. So the more you match, the higher your score.
My own strategy though is to go for perfect matches the first couple of levels, then just hold the fire button down and go for survival (and blocking off skulls) rather than perfection. I'd be really impressed if anyone managed to get every level perfect - that's way beyond my skills (especially the later levels, when aliens turn up and start shooting tiles at random...).
Still looking into the OSX crash - it looks like it's a threading issue with the music, but I can't replicate it on my ppc macmini
It's possible it only shows up on multiprocessor machines, but my dual-core Windows and Linux machines don't have any problems, so I'm kind of stumped.