That is true - the skeletons would be a nice touch. Thanks for the advice!
Yup, I thought that might confuse people. I considered various ways of when to trigger the transition, but this seemed the most reasonable. I thought about moving the camera closer to the player so it'd be barely impossible to walk through the arch without the transition, but I think this has it's own perks and disadvantages. E.g. you can move the player through the arch and move camera around him and see him in both worlds, depending on the camera orientation (which I think looks cool). That's why I spawn arrows on top of the arch (if you don't move through any arch in a while) to help the player from which side to enter the arch.
Anyways, thank you for playing and for this review. :)