Battle, by 
Starling is fun stuff, a bold revitalization of the ancient art of combining JJ1 sets to form new things, but a JJ2 set for a change… the exact reverse of the IC JJ1 episode. And what do you know, it looks great. The deliberately non-fading background is a particularly cute touch, but the layer 4 stuff is still a great mixture of clearly Colon-inspired while not trying to faithfully recreate every single Colon detail. The crates feel appropriate despite not having a clear analog, and the pillars are fine too. I wouldn't have thought of any of this but it's all nifty and clever.
The biggest risk Starling takes is the sewer/coin area, but I don't think I'm thrilled with how it ended up. It just doesn't seem worth it from a gameplay perspective, despite how interesting it is. If you want to go to the roof, you can use the lamposts, even if they are very narrow. If you want the powerup you can shoot it through the wall. The sewer takes a while and feels like a trap to get camped on. It's very interesting but I wouldn't want to go there, although JJ2 players are like ants and I'm sure some people will pass through it anyway.
Outside the sewer, well, I like cramped spaces in Battle levels, with weapons that can reach around corners a bit, and Starling delivers, but with nice smooth walls instead of the uneven alcoves of cramped levels of yore. It's not a silky smooth gameplay experience by any means, but it's consistently interesting, and because part of the problem with the sewer is that it's so skippable, well, you can simply skip it!