Hi everybody! I'm making a master post in which I'm including some of my small works.
The purpose of these carts is to be used live in chiptune concerts as material for vj-ing, so some carts may be actually interacted with.

Please be advised that nothing here is thoroughly optimized and mostly the code is some kind of 'hack' in the worst sense :) all of the stuff is very demo-inspired

Also I have some code background but I'm really unexpierenced in computer graphics and so the stuff you see maybe well known to you but experimental to me, I'm slowly learning mostly by myself and it's very satisfying!

I called this fake amiga ball just because of the ball colors, there is no attempt at making it feel 3d.
You can change the background pattern and colors.

A colorful balls tunnel. You can change the rotation and toggle a manual mode.

I don't know what I had in mind when I did this but certainly not an eyeball. It turned out like this when I made concentric circfills. It's kind of bugged but I like it anyway, you can change the number of orbiting balls and the symmetry of the scene.

HUGE EPILEPSY WARNING ON THE NEXT ONE
This is VERY flashy. You are advised.

Inspired by an analog video patch I've seen somewhere. You can change the number of rectangles and do some silly memcpy.

This one has a lot of stuff! You can change the polygon shape, there is a couple of glitch effects, a B/W mode, symmetry, and by rhytmically pressing X you can set the BPM (a feature I should port to all the others too)

This one is based on one of the pico-8 demos. It looks like a torus somehow.

A cuboid rotator effect. I'm very proud of these despite the fact that there is no texture mapping (which I should work on someday) because I figured out the 2D mathematical process entirely by myself. No big deal, I know, but it motivated me a lot.
You can add a bunch of them and remove the background.

Some particles becoming balls. Low effort demo which someday I'll rework probably.

HUGE EPILEPSY WARNING ON THE NEXT ONE

This one I like a lot. It features random connected points moving. If you apply symmetry (with UP) some cool shapes come out and you can randomize the generation with X. Very very cool imo.

A lot of stuff going on here. You can tweak a lot of parameters, maintain the video buffer with X so that you obtain a cool effect, change the number of balls, symmetry, and apply a cool waving effect. Speed doesn't work AFAIR. Z prints a dot on the screen so that if you combine it with X the screen buffer stops deleting and you get a cool scrolldown effect.

Similar to the tunnel effect in the Overdrive 2 demo by Titan, but a lot lamer. You can change the dimensions of the rectangles in manual or automatic mode (with Z)

A classic twister with a blocky effect appliable, and obviously symmetry.

gravity, basic bouncing, basic reflection with memcpy (inspired by the 'ad astra' demo by 4mat)

a basic doodle a simple background with texture shifting

Please let me know if you appreciate the stuff!

demo graphics fx

Thanks everyone for the answers!
I knew the amiga ball isn't real 3d even if I haven't completely worked out the math involved, but what I meant is that in my demo the palette is applied "flatly" with no depth perception. Thank you all again, you're very kind! Today I tried projecting one of these fullscreen in my room in isolation and it looked great!

EDIT: I added a couple more which I had forgotten