Algodoo

This thing spawns circles in a four-stroke manner when the dark grey circles collide with the red ones.


How it works:

I added a custom variable `_igt` to the red circles. The value of `_igt` is determined by the script in the dark grey circles' `onCollide`, which keeps the `_igt` value between 1 and 2.

The script in the red circles' `onCollide` then makes sure a new circle would spawn only when `_igt= 1`.


This method runs fine when there's only a single cylinder.
Not so much on more cylinders, since each cylinder runs on its own ignition timing despite being connected to one shaft; their firing order is easily messed up when the circles collide in wobbly ways e.g. vibrations, stalling, high RPM, or simply drag and force reversing the engine's rotation.


feel free editing it