Hey thanks for playing! I really appreciate such a detailed response.
In the "too early press" situation you describe, the failure is intentional, you have to input at the start of a measure. I see where you are coming from on wanting a bigger window, but the window is quite large actually (1 quarter note 'wide'), assuming you are aiming for pressing at the start of the measure. I can tweek the penalty and window as people play to see what feels right. Maybe a lives system or something.
From a flavor standpoint, if you are running in the dark, and you turn too early, you may fall into a pit, hit spikes, etc. Thats the idea I was going for, at least, maybe it dint translate.
Nice job finding a bug, I didn't know that happened! I'm fixing it right now! That's good play-testing :P