Real Four-stroke Engine with cylinder (no trig)
This project is based on the same elements of ngrm's "Engine" project http://scratch.mit.edu/projects/ngmr/70365.
The purpose here was to REMOVE ALL TRIG CALCULATIONS, by making only use of the MECHANICAL CONSTRAINTS of a real four-stroke engine (simulated by Scratch's collision detection blocks).
Look at the detailed comments in order to see how the constraints are making it move in the desired way.
-added external cylinder with collision detection