Reaction time. After a random delay of 1.5–5 seconds the box turns green and a high-resolution timestamp is taken; your click or key press takes a second one and the difference is the trial time. Clicking early voids that trial. The score is the mean of your trials — the median is also shown because one lapse should not define you. Typical results for a simple visual reaction task are around 200–300 ms, with a median for online testers near 270 ms; elite sprinters are held to a 100 ms minimum because anything faster is treated as anticipation.

Latency you cannot remove. Your monitor refreshes 60–240 times a second, so on a 60 Hz screen the green frame appears on average 8 ms after the timestamp; a wireless mouse and the browser's input pipeline add a few more. That means every score here is a little slower than your nervous system — but consistently so, which is what makes repeated tests comparable.

Clicks per second. Every pointer-down inside the box counts, from the first click until the timer runs out. 6–8 CPS is a normal fast click; jitter and butterfly clicking techniques reach 10–15. Touch screens count taps. Auto-clickers are, of course, cheating yourself.

Aim. One target at a time for 30 seconds; a click that misses still counts as a shot, so accuracy is hits ÷ shots. Targets never spawn under the cursor and are kept at least one diameter from the edge.

Storage. Personal bests are saved in this browser only. This is a game and a rough benchmark, not a medical or occupational assessment; tiredness, caffeine and screen size all move the numbers.