See attached pic.
Update: Now working on P2 Eval. Source code posted here.
Getting ~37 fps using just one cog on 250 MHz P2 Eval.
But, speed can be dramatically improved (by using more cogs).
Features background, textured walls and textured floor.
Far away walls now a bit darker.
You can see where I got this idea from here: https://permadi.com/tutorial/raycast/demo/5/
I've made some notes on the coordinate system, attached here for reference.