ok dokey ive had a wizz on ya game and i like it ,the stlye of the game reminds me of geoff minter, he programed a lot of sprite based games on the spectrum ,commodore ,st ,amiga e.t.c .
Your own sprite routine is well fast and i like the pixel exsplosion routine all works well and looks ok.and collision detection seems fine thou i only played for a while.
Be interested in seeing your new work!
goodluck.
cheers freehand....