Lights Out.

Start the sequence and wait for all five red lights to go out. Tap the button or press Space as soon as the lights disappear.

Patience is part of the test

The delay changes each time, so trying to anticipate the signal can trigger a false start. Wait for the visual cue.

Measure your own progress

Your best valid reaction is saved on this device. Try several attempts with the same screen and input method to make comparisons more useful.

Model notes

Screen refresh rate, browser scheduling and input latency affect the result. This is a browser reaction experiment, not a professional driver assessment.