There you go: https://vbsd.github.io/chimp-game/
In medium mode, the numbers are hidden only after you click on 1. In hard mode, the numbers are flashed for 210ms. I couldn't succeed with that one, not even close.
The game is very rough and not mobile-friendly though, sorry. I know nothing about front-end development and my interest quickly waned.
Someone wanna slap that game together and share the link? It would be fun to self test what the chimp was doing. Still though, really amazing to see how similar we are to them.