I have to start by saying, as a math geek, I love this concept. Using the imaginary numbers to represent your "it is not real" theme is beautiful. On top of that, being able to switch dimensions is very cool, and the art is badass. Flying around with the Blink power was cool too. Easily the best part is the aesthetic, the art is super cool and fits the theme of the game perfectly.
I only have a few issues: first, my gun doesn't actually seem to work, so I couldn't progress past the first level. My damage was 6 + 6i, so theoretically I should've been doing something, right? Let me know if I misunderstood.
Also, after I die, I can't go back into the game - it keeps showing me the death screen, so I have to restart the game to try again.
Last issue is the sound. I really like the background music, I think it fits the vibe perfectly, but for some reason there's a really grating sound that happens after playing for a few seconds. I think it might be from projectiles or me getting hit/hitting enemies, so not sure what the actual source is for it.
All in all, I think it could use a bit more tweaking, but it's easily the best concept I've seen so far. Let me know if you decide to flesh it out, I'd love to play it.