Thanks for playing.
I did put up those signs to explain the mechanics but never got around to add a prompt to indicate that you can read them so seemingly no one does. Woops.
One thing I noticed with your gameplay and others' is that even when they figure out the "double jump" mechanic they keep trying to use it very up close to a platform whereas the trick is to get some distance and I still have no clue how to communicate that to the player. I don't wanna put it on a sign because those should just explain what the mechanics are, not how to use them efficiently. That should be done by level design but I just haven't found the right design for the first level I guess.