Semi-on-the-fly remarks:
- I like the clouds. :) And I tend to like sky settings, it feels a bit otherworldly and dreamy.
- Controls are QWERTY-only instead of layout-independent (I have an AZERTY keyboard).
- 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.
- Ah, different music for different levels! Or when you reach a new cycle?
- 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!
- 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!).
- 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
- 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.