Things are about to explode!

Two very brief sessions over the last few days.

Player lasers and alien explosions are all-but-fixed now. I've realised that I need to go back and review all the reference points used for the rotation again. But it's something I'll leave until all the rendering routines at least look correct, even if there are some minor alignment issues.

I've also been able to re-use some of the object-specific rendering routines for multiple objects, so I'll have to go back and rename some of them at least.

The game is playable now, albeit with occasional graphics glitches. The oustanding issues are UFO explosion, player explosion and invader bomb explosion (hitting shields and/or bottom of the screen). And shield orientation of course.

I would hope to have these issues sorted by the end of the week, though it depends on work/family/exercise/sleep commitments.