Some comments:

1) Experienced cases where the enemies would glitch through walls / pierce barriers or even exit the playing field. This made the game easier in most cases but could also cause some levels to be incompletable.

2) It would be nice to indicate that the wasd keys could be used to control instead of the arrow keys

3) Noticed some lag between inputs affecting the action on screen which could cause one to get killed

4) It would be good to note that space bar is used to bring up a help menu which includes the important key "R" for restart (I didn't know about that when I got stuck on Level 22 or Level 23)

5) Hitting Q to return to the menu had a slow response to the point I wasn't sure if it was working or not...

6) After finishing Level 24, there was a bit of delay before returning to the front page which gave the impression that game hung.

However, overall an interesting and fun puzzle game.