First of all, thank you for using Tetra! It's really exciting to see a finished game using it, and your feedback over the course of the jam has been really helpful :D
That aside, here's my feedback:
* The art is extremely cute, and definitely evokes the vibe of those old handheld/mobile games. The end screen in particular made me smile :)
* I liked the game mechanic - I had a good 'aha' moment when I realized what the pickups were allowing me to do!
* The controls worked well - the way the back of the character's tail would get out of your way when you reversed direction was nicely done. I imagine it'd be quite easy to overlook little details like that with a tight deadline, so kudos :)
* It'd be nice if there was a way to restart the music once you've stopped it (that said, we discussed this on Discord a bit and I definitely could make this easier in the engine's API). Also, there's a bit of a delay between the game starting and the music starting - is that in the audio itself, or is that a bug in Tetra?
So yeah, slight audio quirks aside, a big thumbs up from me :)