interactive

An uncommon situation that occurs at the boundary or extreme of normal usage — an input field left empty, a user clicking twice in rapid succession, a list with a thousand items. These situations don't happen often, but when they aren't accounted for, they're usually exactly where an interface ends up looking 'broken.'

A single trigger-response pair where the interface answers a specific user action with a small, immediate visual reply, so the user knows the system registered the action instead of guessing whether it froze.

A placeholder made of gray blocks that mimics the final page layout before real content finishes loading, letting a user see roughly what the page will look like ahead of time — it shortens the perceived wait, not the actual load speed.

The mechanism that tracks what condition an interface is currently in after a user interacts with it — how much of a form is filled in, whether a toggle is on or off, how a list is sorted — the key factor in whether a prototype can actually be operated like a real product.