It's been a very long time since I last played it. It feels really janky at times, but it still pulled me in enough to play late into the night.
I think water currents (or whatever that is, this is not just my imagination, right?) should be way more visible, because of how much they can affect movement. Then, there is a LOT of visual noise. The graphics are beautiful, but I often have huge trouble with figuring out which level's elements will collide with me, and which will not.
Then there's the physics. At times movements aren't responsive, like it's a weird physics thing (without water currents, or other effects). Maybe I'm just bad at placing movement nodes, but I guess it could be more consistent. Levels have a lot of very tight passages, and it's easy to get caught by random map geometry, so I feel encouraged to not build anything past 3 zooid width.
And god damn, that brood level was terrifying. The risk of chain reaction keeps you on your toes, and the creatures flip flop between full aggressive suicidal attackers and running from you around the map. I don't think it's a good idea to have them escape like that, since it's an absolute pain in the ass to chase them, and killing them seems required to progress.