The easiest way to lie with a demo is to record it once, clean it up, and loop it. We did not want to do that. So we wore the thing during actual work.
We ran it during coding sessions. We ran it during Dota 2 matches, which turn out to be a great stress test because focus swings hard and fast. When a fight started, the score moved. When we tilted after a bad death, you could see it drop.
The traces were not pretty. Real EEG never is. There is drift, there is muscle noise, there is the moment the electrode shifts and the signal goes to junk. That is why we built gates. If the signal is bad, the score freezes instead of showing a fake number.
We also learned what a focus number cannot do. It shows what happened, not why. A hard part of a game lowers your focus and also gets you killed. The score and the death happen together. That is a link, not a cause. We try to be careful about that difference.
Testing on ourselves kept us honest. If the number did not match how the session actually felt, we knew something was off. And we fixed it before anyone else saw it.