Thanks for the feedback!
Yeah, didn't have time to do the proper playtesting. It was my first game and a made it in several evenings after work. So I decided that finishing it is more important than polishing it. And too late I understood that I had to make auto-shooting =)
As for pixel perfect yes, as I googled later, this is a common issue. And Unity has a blogpost about that https://blogs.unity3d.com/2015/06/19/pixel-perfect-2d/ , as well as there are bunch of articles and videos in the Internet. I haven't tried these by myself, though.
Here is one more explanation why is pixel art might not look smooth in motion https://stackoverflow.com/questions/35785291/getting-giggly-effect-when-slowly-m...