Heyo~
I think this is a really solid platformer, I had a lot of fun while playing it. I liked the risky element there was to picking up gems and how much it changed how the user must interact with levels.
I do have a couple suggestions. The first one is a pure style element, which is to allow the user to replay levels by walking through the portal in the game over screen. I took a little bit of issue with blackout, I don't think the effect is necessarily bad but I think it lasted too long and ended up being more frustrating than challenging. Finally, I think that the user could use an easy introduction or do with more visual clarity as when I encountered them for the first time I didn't know they were spikes and died.
Like I said, I think that your take on 'powerups' was really fresh and added a lot to the game and that it matched the theme in a fun way. Well done :)