Hi WifuWaffle! There are two causes which might be the issue - one is that the framerate doesn't run super fast in some browsers, so you can definitely try it in another or download the PICO-8 version (if you're willing to spend $15 on the PICO-8 Fantasy Console). There's also a chance that your jumps aren't working when you run off a cliff because I didn't program coyote time into the physics here. My future games will all have coyote time though, so that will help in the future!
Thanks for giving the game a shot. :)