Build 23 is now live and includes the following:
Major visual overhaul!
- all levels now have proper floor tile details
- main and transition levels have some extra background details
- improve boss particles, align lighting colour with animation state
- add some background animation (spinning fan blades)
- spinning objects now have a little "anchor" point rather than just fading to nothing

Other changes
- fix for some particles escaping (or getting stuck in) level geometry (blood, boss impact, steam)
- minor changes to main level generation, plus some special surprises in the transition level progression (you'll see...)
- simple lefty support (A/D for movement, however, W/S not implemented for looking up/down yet)