That was really neat! I've always liked the idea of endlessly jumping endlessly on a trampoline just for fun, and I think this game encapsulates that feeling pretty well! Plus spreading out a few coins here and there with some smaller trampolines was also pretty amusing! It's not mind-blowing or extremely original, but it served for the bit.
Considering the level is quite long, I'd have liked to see some check-points here and there. Early on when playing I was trying to go for all coins, but as I'd eventually hit lava on the corners, I'd have to start all over again. That got repetitive after a while, and I just decided to go through the rest of the game. Having some check points here and there that allow the player to keep their progress before a new hazard is introduced (like the moving lava blocks) would have been great.
Another thing I would have liked is for there to be some sort of indicator of where the trampoline is if it's beneath the lava. Something like a ghosting effect just to make sure you're timing the trampoline off the lava at the right time. Making sure the trampoline is clamped to the screen-view of the player so that it doesn't move off-screen would have been nice too!
As for the high-pitch sound, I didn't pay much mind to it, as that issue sometimes happened with us when making WebGL builds. There's no real way to fix it other than trial-and-error with re-encoding the sound with something like Audacity and trying to build again. Though with some perseverance, you will eventually get it sounding as its supposed to. Cheers and here's the best to Jumpy Trampoline boing boing skippeti skippeti jump! 🐳