Enjoy! Don't forget you can use Cheat Engine to train at slower speeds if It gets too fast and work your way up.
I try to never advise cheat engine... never know what other games & anti-cheat or DRM system the player has on their computer.
I'm not sure what you mean. Super Hexagon on GOG is DRM free and because it does not have working leaderboards like Steam there is no darger of cheating online against other players. Cheat Engine lets you slow down Super Hexagon so you can train when it's too fast for you, until you can practice a level at full speed, or more if you wish. You want to close it when you play online as it could get you accused of...well, cheating. I had a lot of fun with it with SH and never a problem. Sometimes it's great just to play a "zen" and relaxed game. :)
It's a pity the game does not have an easier difficulty so I suggested a way to get it, rather than having to give up!