I would like to mention a few things
1.The enemies being able to go through walls but their bullets cannot( i know this might be a bit unbalanced if the bullets go through walls but i find it kinda odd)
2.The tutorial and story being told by a wall of text, i find it kinda boring to read, maybe you could add some illustration image to illustrate the text so people can understand it at a glance.
Other than that in my opinion its very great
the music is great, and the concept of sacrificing time for in game benefits is very creative.