It took me a little while to realise that I was controlling relative buoyancy rather than vertical movement with W and S (my bad for not reading the instructions more closely), but once I worked that out, I thought this was neat! Similarly, I thought the crayweed was cosmetic decoration until I re-read the instructions after playing a few rounds.

Sorry to hear that you got sick - I hope you didn't push yourself too hard and that you're feeling better soon!