The guards move around too quickly, so they turn CONSTANTLY in small areas. makes it nearly impossible to get around them. especially when there's 4 just randomly bumping around the manhole >_<
It's too easy for the down-blocks to absolutely wipe out any path higher, while it forms a ceiling and you get eaten.
Really, my only complaint. the rest, the idea, it all owns except for that.
bugs: can fly off screen, making invulnerable, but able to continue shooting. death is continuous, meaning it keeps trying to play until you die 5 times as you fall off the screen with no health. levels somehow skip, played lvl 7 after lvl 1. asteroids not affected by "kill all" bonus, so half of bonus crates absolutely useless. lvl 4 ends without a continue screen. lvls 8-15 not available. have to play lvl 1 again to grey it out. also, stats bar needs to be above everything else on your layers, and i suggest a double layered background, so the mothership is behind the buildings, but not the sky. and might help to finish it, you can test it yourself extensively before uploading it on a site. just a reminder that this is a GAME site, not a TESTING site.
the simple fact that you expanded on the shootorial, and 95% of it is your personal artwork, not outright theft from shootorial, makes this a decent game.
if you listen closely, you can hear the in-frame music, while you're out of frame. makes a really neat sound, mixing the subtle out-o-frame with the more upbeat in-frame music.