Hey,
no actually we didnt do anything special to optimize the game. However the games architecture is based on the "Observer Pattern", which removes a lot of the dependencies and the need to do a lot of code in Unitys "Update" function, which is called every frame. So in the end there is actually not that much code executed each frame, which keeps the framrate quite stable. We didn't primarily do this for the optimization of the game though. It just leads to nicer and cleaner code.
The only thing that causes a bit of lag are the numbers that popup, because they are getting instantiated every time a cursor clicks the cookie, which happens quite a lot. We will probably fix it by using Object Pooling.
You can also take a look at the repository, which is linked on the gamepage.
Cheers!