Came back to this game after half a year and it's still so good, I just found the hidden endings yesterday. I'm totally lost on the directions supposedly hidden in Pool 1 though, can't wait to find them and explore the three other pool rooms!
Edit: turns out I was obnoxiously oblivious for a couple months, because I just found the codes in pools 1, 2, and 3 in a few minutes. Currently seeking out the one in 4.
Edit two: I've only got Pool 4, "Be Fast", "Your Jumps Are Annoying", "Pick Up the ???" and "Locked- unknown" left. If anyone sees this and has cracked these locations please do leave me a tiny hint! Thanks!