Absolutely fantastic. I don't even like single-player games that much, but this one caught my attention. LOVE the art, and the gameplay is surprisingly in-depth for such a simple concept. My only gripe is that certain abilities are way overpowered IMO. I was struggling to get to the boss until I began a run with Bubbles, and from there I got some good upgrades and just destroyed everything. Felt good though! :D
(EDIT: ALso, excited for the mobile version, and more content :D)