Hmm, I thought the problem was that the acceleration of the car (for example sideways acceleration when going through a bend) was perceived as a sideways compon

Hmm, I thought the problem was that the acceleration of the car (for example sideways acceleration when going through a bend) was perceived as a sideways component of gravity – as the principle of general relativity tells us, they are the same thing – without there being a corresponding visual input, even when looking outside. In contrast to something that replicates the actual horizon, the blue liquid in these glasses would feel and adapt to the same sideways acceleration as your body feels, so I thought that was the point.