There are some simplifying assumptions that may help with some of your questions: > What would happen if he switched back to the normal 3 dimensions in the mid

There are some simplifying assumptions that may help with some of your questions: > What would happen if he switched back to the normal 3 dimensions in the middle of the wall? The 4D cell the player is in is clear, no matter how you rotate the world around them. The cross-sectional representation of the world can misleadingly show you things you (and light) can't reach, though. > In miegekure everything is kind of discretized (grassy area to desert area), but in reality that would be continuous. It's as discretized as Minecraft, but with an extra dimension. In Minecraft, you can't simply go through things, just as the Miegekure won't let you. > What would that actually look like, for example, the area right next to the wall? All common representations of 4D space show you a cross section or x-ray projection, which, as with such things in life, show you internal details you can't see with visible light. Unfortunately, there seem to be no realistic representations available. > if I were sitting in an easy chair and started looking down the 4th dimension what would happen? There's no way to answer that without knowing what you're actually sitting in. An easy chair is a 3d object and a 4D you can't sit in it. > How does gravity work in those 3 dimensions (2 of our spatial dimensions + 1 of the hidden dimension)? Locally, remember that gravity is pretty much just a constant force in a particular direction. That works in 4D, too. If you're looking for physics answers, the answer is that most such forces would be incredibly weakened if they dissipated in an extra dimension. > For example, since the three dimensional projection of a hypersphere changes diameter, does that mean the 4d dimensional analogues of earth are just different size earths? This is answered in the Matt Parker video linked to in another reply. The shape doesn't change diameter - that's just a feature of the physically unrealistic but pretty representation that's most common. It could be called a shadow or projection. > in one of the miegekure videos the windmill in the new 3d space is like a cross section of the windmill but extending for a distance Remember that for it to exist in miegekure, it has to be a 4d object. It is one that has been chosen to look like a windmill in a particular cross-section. In other directions, the game designer simply chose how it behaved. It is, in essence, not a windmill, but something carefully made to look like one when looked at in one particular way.