I was thinking about making the crystals reflect based on movement, since the light source will have to move relative to the camera to get that effect, but I'll have to see that in motion before I decide on anything. If the point is to make them visible, only making them change when everything else is also in motion might not work very well.

Yeah, I like this idea. It's easy enough to implement (see also: those player-tracking eyeballs devs loved to stick in their games in the early-mid 90s) and makes sense since the player has that light on his head. They could shift relative to glowing enemies too, acting sort of like an enemy sensor. Hey, Out of this World did it.

As for the drab paper, have you tried something like dithering the gray with a color like yellow for a faded notebook look? You can play with the pattern a bit for texturing, add yellow/white/gray lines for creases, etc. My quick attempt:

(compare to )

I experimented a bit with the text to see what was most legible on that background. Gray outlines were too much, but a simple gray drop shadow to the right or left works nicely. Nice pixel font, by the way.

If that's too strong, you could try 1/4 tone dithering, or cyan or blue dithering maybe.

The back half of the rat looks really good. The hind feet seem to stretch out over 2x, though. The front left paw seems to move too much all of a sudden, and that hanging jawbone interferes with the apparent motion of the front legs. I'd try a version with almost stationary closed jaw and see if that doesn't help with the leg confusion issue.

Which is which?

I like using Idraw, it has a simple animation feature.