A really nice retro themed puzzle platformer. The platforming felt solid, and the swapping mechanic was seamless. The graphics were well put together as well, with the sprites working well for the retro aesthetic. The little juicy things (like the subtle screen shake and thud when shifting dimensions, or the background shifting based on movement) gave everything a really polished feel.
It's hard to come up with any constructive feedback on this. Everything that it does it does well. It could do with some extra stuff like being able to see the other dimension before shifting (so I don't have to die a few times shifting to figure out the map), or an in-game tutorial (some button prompts in the first level), but overall I enjoyed what was here. Just give me more levels! 😉
I also respect the choice of using Pygame. Keep up the good stuff!