Just noticed this yesterday, and had a blast messing around with them in objectplace! This honestly deserves more attention, because any effort to give this game more Badniks is always appreciated! The Spritework here is good, and the Badniks themselves have the potential to be used very effectively!
There are a few minor tweaks / nitpicks I'd like to see addressed before people start using them in levels.
1. Compared to the original game: Motobug, Spikes, and Blue Newtron all move too slow, and Burrobot moves too fast. I'd suggest swaping the speed values of Motobug and Burrobot, And giving Spikes and Blue Newtron a speed value somewhere in-between that of Motobug and Burrobot
2. I think for the sake of being in a 3 Dimentional Space, Crabmeat should fire his projectiles in a circlular radius as opposes to just 2 directions. This will allow his attack to be just as threatening to the player in 3D as it would be in 2D
3. I was kinda disappointed when I found out Caterkiller doesn't split when hit from the body as opposed to the head. If you end up adding this be sure to have the segments disappear after they bounce for a while, to simulate the effect of the object despawning when it goes off-screen in the original and for the sake of net-games
4. BatBrain's flying animation feels static. I'd recommend adjusting his offsets to give him a similar bounce to the one he has in Sonic 1. Aside from that, I noticed his D3D7 sprite has a stray pixel floating in the upper left-hand corner of the frame! It may seem minor, but trust me when I say people will notice it and be bothered by it if you don't fix it.
All in all, fantastic work on this, and I'm excited to see what more you'll do with this! Perhaps some S2 or SCD Badniks could join in to make this a sort of "Classic Badniks" pack?
