It's a simple, addictive little thing that manages to develop a really interesting, vaguely unsettling atmosphere over its handful of areas. "Bullet hell tennis" is a really strong concept in and of itself, but I can appreciate that there was clearly a (mostly successful) effort here to say something and have a neat little minimalist, kind of meta story to give the player an incentive to see it through to the credits. Also if you're interested in this game don't look at the trailer because it spoils something kinda neat that happens towards the end