Damn! This is a really good game. I mean seriously good. If I bought this on steam I would be very happy. Brilliant concept, excellent voice acting. I loved the particle effects and all the floating, spinning symbols, (how did you do those by the way?).
I played all the way through and only had one or two issues with gameplay. Mainly me being rubbish at the gravity well tool! Other than that I got into a really neat little flow state with the bridge builder and I felt like I wasn't alone, thanks to my little floating buddy, so top notch theme usage.
I would really love to see more from you. This game felt perfectly self contained so maybe another project which utilised a similar approach would be cool. Expanding on this core idea.
The level design was textbook! As in you used things we have been taught in our level design module at uni. Leading lines and great use of verticality lead me through the whole experience seamlessly. I was never lost but I also had a sense of awe and exploration throughout. I think people should give you some excellent feedback on this project.
The story telling worked really well here. The slow build and the gradual introduction of new gameplay mechanics, accompanied by story beats was beautiful. I was engaged from start to finish. I would say a little adjustment on the check points might be good as I did find myself a little further from my point of death than I would have liked at times. Other than that it was awesome!
One last thing is that I felt your use of particle effects, mixed with sound effects, (and screen shake) really sold the power of the lightening. You managed to make so relatively simple visual elements work exceptionally well. Congratulations! Great work, and I can't wait to see what you come up with next.