It has come to my attention to make an improvement over my Gunstar Heroes animation routine, after my current routine has been a pain to work with.  My old engine required every animation frame to stored as either a 64x16 or 128x16 chunk of sprite patterns, which made it difficult to add sprites to my game, due to manually compressing every sprite image in my game.

So I am implementing variable slot height, so the sprites in ROM can actually look like they do onscreen, instead of a jumbled mess of 16x16 and 8x8 patterns.  It would then be possible to write a routine to automatically generate the ROM addresses of an animation, without using pages of look up tables.

If you have a lot of the same enemy on screen, isn't it quicker to just have a timer for each enemy that you increment in the NMI instead of having to update the VRAM of every enemy sprite? What are the advantages of updating the VRAM? Anyway, do you have any demo ROM or source code that you would like to share?

I chose to update animation on the fly incase I run out of VRAM in the future. I got it to work in my Gunstar Heroes game, but it is a bunch of spaghetti code.