woah, thanks

Control surfaces using large rudders on spinblocks that react to pitch command can be used with a PID controlling pitch using pitch as input, with a fake value of zero. That way, when you advance, the control surfaces will keep your pitch horizontal.

As for control without lua, you can use PID, air pumps and control surfaces.
Have a hull without air pumps, make it heavier until it sinks. Then add air pumps at 100 % and make the hull lighter until it floats. Between these two masses, your submarine will work. Just use a PID to control the air pumps using the altitude as input, and use a fake value of, say, minus 50.

You can check the submarine here: https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1923712392

oh ok

No, I mean programming the computer yourself. I've got 4,000+ lines of lua code in this submarine. :-P

oh, nice. i'll experiment with AI and see what i can make

That's because you don't have a proper navigational computer. It's much simpler when you select on the right-side map the point where you wanna go in Neter and input the depth, that way the computer does it for you. Easy! :-D

and i cannot even keep a submarine pointing in one direction for a second