Ohhh interesting question….
I would have to say that I think it’s possible to use treadmill, package delivery rails and hydraulics to make a movable floor so that VR gaming and work outs would be hyper-realistic.
That’s an interesting and difficult question which I’ll give a simple answer to: a computer. It may not be the answer you were looking for, but I think that it’s almost impossible nowadays to invent something completely new without using a computer at some point in the process, whether it’s for modelling and simulation, testing, or training (in the case of machine learning). Of course, you can always use computers to design better computers as well!