I’m glad I could add the different modes. They don’t really change much, but peaceful is nice if you find the oxygen stressful. Speedrun was more for me, I like to speedrun my games once I get close to the release!
The metroidvania route is definitely what I like, though I do like how I made most of the upgrades optional (technically the shovel is the only required item).
Someone else mentioned Scuba Dive for the ZX Spectrum as a similar game, and looking at gameplay I do really see the resemblance. I think you are meaning to say Animal Well rather than Animal World? Animal Well (and its so-called “metroidbrainia” genre) was certainly an inspiration. I like having knowledge-gates in metroidvanias, it’s just a very tricky thing to design!