itch.io

I uninstalled and re-installed. The jump still seems random, but is working much better. 

EDIT: Scratch that, when I use ShareX to record my screen, jump works better, but if I stop recording, the jump stops working reliably. 

Negative. Installed locally on Windows 10.

Game appears interesting, however - none of the three jump buttons (up arrow, spacebar, or W) jump high enough to interact with the menu. At random, they will, but then a portal appears making you have to jump again. Had to Alt+F4 to quit the game.  Bummer.