This was fun, but also a little stressful trying to understand the controls while I’m already getting blasted from all sides :) Didn’t get the envelope/paperplane difference either, and accidentally discovered the boosting with Space.
Also didn’t realize about the mouse controls until reading the comments here! Went back and discovered there’s a few more things to the game, and then I won after two attempts.
Minor bug: sometimes enemies/power-ups spawn outside of the playzone and stay there.