Interesting concept, easy to get to grips with and understand after completing the tutorial and playing a round or two!
I understand that this may be a simplified version of the games' aesthetics, but the minimal approach is appealing, adding some futuristic effects and audio would compliment this well.
Using W and S felt a bit odd since most games opt for the space bar as a jump, but that could come down to my personal preference.
There was a lot of text in the tutorial regarding power ups, I didn't read them on my first play. I saw the word power up and understood what it meant.
The UI could do with being bigger or not being there at all in the finished game.
Overall, I look forward to seeing how the game develops :)