Thanks for the feedback, this is gold!
For the keyboard controls, playing in a browser window brings up some unique constraints. I'm thinking a good layout that will not only work for right and left-handed players but also work in a browser window could be spacebar, J and K for jump, fire, and dash respectively. I talked to an experienced keyboard gamer in person and he that's the best option but would be better to implement a customized controls screen. Probably change the defaults for now and add the extra screen later.
The shield powerup was intended to be an actual force field shield thing that could block 100% of attack for a second then have a cooldown time. I had made perfect activate/deactivate SFX for it but the animated sprite wasn't working out how I wanted it and eventually, it had to be cut for time and was coded as a 50% defense bonus.
Other upcoming changes are: more useable charged weapon attack, save slots and checkpoints, shield powerup implemented as intended, more level hazards(one such hazard is a high voltage discharge thing that must be turned off with a switch elsewhere). For a full final actual release version I would also like to fill it out to 10 total levels/biomes with integrated story beats and maybe a few cutscenes where appropriate.
Good things coming!