Field test
Your score is right minus wrong, so hammering one key is worth nothing.
Click a colour or use the keyboard — 1–4 for the four colours, or ←→ + Enter.
The four buttons are labelled with colour names as well as colour, so the test is playable without colour vision.
The server times the run on its own clock and re-derives every trial to score it; a run that could not have been played by hand is flagged and never ranks.