Absolute joy to run through with the different enemies and their increasing number and speed. Simple random levels with interesting enemies and the meaningful bonus of a map you could find. Actually fun to play and a personal favorite!
I do think that, because it eventually gets to a point where you cannot avoid damage (like, level 15 enemies and higher sometimes seem like inevitable damage), having an end goal or boss or something MIGHT be cool... but then again random dice rolls make every situation a possible win and race against your luck.