Most of the levels were made on the last day with a very tight schedule, so balancing was the last thing on my mind. Definitely should have spent more time on a proper tutorial and a more gradual difficulty curve. I also only play using WASD on basically every game, so if someone doesn't remind me to also include arrow support, I just forget about it.
I'll try to fix the tutorial and arrow problems on the revised edition. Not sure how much I can do for the difficulty curve but I'll give it a shot. Thanks for playing!