Well put together, would recommend a bit of tutorial. (showing controls) but other than that very good.

really really cool game, well thought out puzzles and good visuals, great job!

Nice puzzle game. In my opinion, it would be nice to have some sound or at least visual fx on death, and also some animations for movement. Anyways, great job!

Really enjoyed this, great interpretation of the theme. 

Great work. Level design is very good. I like it

Nice! Pretty tough puzzles!

Pretty decent one Congrats on submitting! All the best. 

Such a well worn idea, beautiful graphics and a challenging gameplay. Congrats!

Semi-on-the-fly remarks:

1. I like the clouds. :) And I tend to like sky settings, it feels a bit otherworldly and dreamy.
2. Controls are QWERTY-only instead of layout-independent (I have an AZERTY keyboard).
3. Suggestion: I think adding interpolation to the movement (ie showing the smooth transition from one tile to another) would add to the clarity and visual comfort for the player.
4. Ah, different music for different levels! Or when you reach a new cycle?
5. Bug: in level 4 or about 4 (the first one with a gem), going up from the initial position makes the left crate move up instead of resetting (the right crate is below spikes). I suspect this is because the resetting operation come right before the program handles movement!
6. By the way, I think showing the number of the current level would be nice; also, general tip for playtesting games and especially puzzle games: allowing the player to skip the current level (or choose any level) is a good idea to prevent him from getting stuck (either by his fault or yours!).
7. Oh, found a bug (in the first level to have both a spiky crate and a switch at the same time): once one of the crates has reached the portal, if you switch crates (with Space), the game considers you won the level!! :o
8. Beat the game! :) The last level was great to show what switching the two crates could be useful for. Ideally, a level where you have to switch multiple times would even better demonstrate how the mechanic is interesting.

Takeaway: I had already seen this idea of dual entity control (Bad Link comes to my mind as a recent example), but the possibility of switching them is a nice spin. Graphics are cute. I think adding some details like just some more sounds (for failure and winning a level, for example) and smooth movement would be a nice addition. The big challenge for the game would be to design some levels that would make more use of the main (and secondary) mechanic, although you already have enough for a demonstration + tutorial prototype. :)

A good base for a puzzle game, thank you for it.

Nice one. I liked this and it made me think. Maybe so VFX to make death a little more obvious would be nice. I didn't realise I had died a couple of times at the start. Other than that it is a neat game. I liked the clouds and the slick menu system. Good work! Nice to see an Unreal project too.

Cool game!

There were a few implementations of that principle and this one is one of the better ones. The assets you chose fit the gameplay well and make the entire game feel immersive.

Nice game! Good job!

This is so cool! It's like sokoban with a twist! Such a cool concept! Art was pleasing to look at too! I had a glitch on the final level unfortunately where the regular box would move through the barrel, but restarting the game did fix it. It also took me a while to figure out spacebar switched the boxes, that should probly be communicated a bit better.

Fantastic design! Thanks for making this!

Really fun! I really liked the puzzles!

Fun game! I like the graphics and audio. Mechanics are nice, but it'd be cool if you added more differences between characters. Overall, great game!

This is a funny puzzle game, well designed and tuned I would be happy to see this project continued following the game jam!

Cool! I liked the graphic of the game

Very cool! It would be awesome to see an expanded and extended version of this!

Fun and creative! Multiple mechanics added some depth to the concept.