Since I had already finished the vanilla games a few times, I gave Revision a try. I noticed that there were settings/achievements for completing the game with various restrictions, like not using any upgrades, having a reduced inventory, dropping everything in your inventory before each chapter ends, and so on. So I decided to do a run with every restriction on the highest difficulty, and it turned out to be really fun. Makes you approach the obstacles in an entirely new way, and even turns some previously very easy things into actual challenges. The only problem is that I think that it will feel too easy when you go back to the regular gameplay, without the restrictions.