A gorgeous little game, it's got a lot of character so far! Reminds me a bit of Fez.
I was curious about whether this was intentional or not; I messed around in the game on my laptop using general WASD + spacebar controls and was able to double jump (albeit inconsistently) by pressing W and then promptly pressing spacebar. I'm not sure what your plans are for the platforming development in the future, so if this was an unintentional feature I thought I'd let you know!