Ryan Clark, Founder/Designer/Programmer at Brace Yourself Games

for debug reasons I was logging data that showed how far off the player was from the beat, each time they moved. From looking at these logs I noticed that players naturally drift away from the beat when stressed, then drift back toward it afterward. As mentioned above, they would sometimes miss a beat due to this stress and get frustrated, so I used a leaky integrator to implement an “autocalibration” system. If the player is moving a little faster or slower than the beat, the game will slowly shift the effective position of each beat to match. This can only be pushed so far, but it does help to ensure that the player doesn’t receive a “MISS” when they feel like they were indeed on the beat.

My reasoning was this: A player hits the key when they perceive the beat to be. They might be wrong, but that’s where they feel that the beat is! And if the game tells them that they’re wrong, in the heat of battle, they get frustrated. So this autocalibration system bends the rules a little (without drifting more than 1/2 beat away from the true beat position) to give the player as much benefit of the doubt as the gameplay rules can bear.