I do like scroller shooters. I got to the 2nd boss, and noticed there that the lives system is a little different than others. I suppose it helps with the run though, but you do burn through them with no way to get more health at a boss. And the bosses are pretty bullet spongey with not much variance to their attacks. Usually bosses that tankey will have a 2nd phase or something. The difficulty is good IMO but you should add an easy mode. Also for sure you should redraw the background at a much higher resolution