Give every action a reaction

Why this rule exists

An interface that does not respond to a tap or click leaves the user in the worst place there is: unsure whether anything happened at all. That uncertainty is what produces the double-click, the repeated submit, the frustrated jab at a button that was working fine the first time. Every action a user takes deserves immediate, visible acknowledgment, a state change on press, a spinner, a confirmation, a result, because feedback is how the interface tells the user it heard them. The reaction does not need to be large; it needs to be immediate and unambiguous. Silence, by contrast, reads as failure even when everything is working, and a user who cannot tell whether their action registered will assume the worst and act on that assumption. Responsiveness is not decoration. It is the basic courtesy that makes an interface feel alive and trustworthy rather than dead and uncertain.