Every physical button you have ever pressed lies a little. When metal contacts inside a switch close, they do not make one clean connection. They bounce, rapidly touching and separating for a few milliseconds before settling. To a fast enough circuit, one press looks like several. This phenomenon, called contact bounce , is why engineers write debounce logic, and why your old mouse may suddenly start double-clicking on its own. What bounce looks like If you put an oscilloscope o...