I Built a Piano Trainer That Measures Stability...

Most piano practice tools measure speed. Some measure note accuracy. Some turn practice into a game. Some help beginners learn what key to press next. But there is a problem hidden underneath all of that: speed is not the same as control. A pianist can play fast and still sound unstable. A trill can be quick but uneven. A repeated-note passage can look impressive on paper, while the actual timing is wobbling underneath. And that wobble matters. Especially in repeated notes, trills, and high-pres