It feels wrong to criticize levels for being too short since length is usually a decision informed by the song used, but Aster definitely doesn't make the most out of its scant 60 second runtime either. Everything in Aster is structured very loosely, which is something that works best if it's in service to a broader characteristic, especially in demon levels. Although this might be an unfair comparison, one very successful way this might be accomplished is with a gesture towards awkward or open-ended design, like in Hollow or Grebeworld respectively. In Aster, this awkwardness is definitely present, but the sort of friction it adds lends more to flimsiness rather than memorability. The gameplay in Aster is definitely a contributor, with a lot of things that look outright arbitrary until you realize skipping them leads to dying to invisible objects, but the visuals are arguably just as flimsy in execution. There's undoubtedly a theme running, which is beautifully established in the first ship (by far the best part), but considering how few foreground objects there actually are Aster feels simultaneously aimless and busy. I actually thought I ran into an unavoidable bug towards the end because of how little direction to the player Aster bothered to offer. Polarizing has taken this sort of effect work to much better applications, especially in 2.2, so with how undercooked Aster is I'd mainly refer to it as a relevant creative milestone.