Note that if you use the itch.io desktop app on Linux, it doesn't seem to include the 2016 latest patch for Super Hexagon. Check the CREDITS first screen - should say "PORT BY ETHAN LEE" if it's the latest version. If it doesn't say that, download and install the linux-01082016.tar.gz patch from http://www.flibitijibibo.com/patch/superhexagon/ (there's a Patch.README.txt at that URL which gives a changelog and instructions). You basically extract the .tar.gz inside the ~/.config/itch/apps/super-hexagon/data dir.