MATCH is a free Stroop test you can play in your browser. The Stroop effect — first measured by John Ridley Stroop in 1935 — is the cognitive friction you feel when the word RED is printed in blue ink. MATCH puts that conflict on a clock: tap fast, tap right, override the impulse.
MATCH is part of killpipe brain games, six free daily workouts. Stroop performance is a clean measure of selective attention and cognitive control — exactly the skill you lose first when distracted or tired.