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Tap the ink color
A 30-second Stroop test. Don't read the word — tap the button that matches the color of the ink. Your brain wants to cheat. Override it.
A color word appears in the middle of the screen — for example the word RED painted in blue ink. Your job is to tap the BLUE button at the bottom, because the ink is blue. Ignore what the word says. You get one tap per prompt; correct = +1, wrong = 0 and you move on either way. Score as many correct as you can in 30 seconds.
Look at the word last. The instant you let your eye land on the letters, your brain pre-reads the word and biases the answer. Train yourself to glance just below the text — peripheral vision picks up color faster than your reading pathway picks up letters, and the answer is in the color.
Incongruent prompts (word and ink disagree) take roughly twice as long to answer as congruent ones (word and ink match). When you see the same color twice in a row your timing drops fast — but the next incongruent prompt costs back almost all the time you saved. Don't get cocky on a streak; the streak is the trap.
Finger-park between rounds. After each tap, snap your finger back to a neutral position about an inch below the four buttons so all four are equidistant. The two-button setup most beginners drift into — right hand parked over red and blue — costs you a full hand-shift on every green or yellow answer.
Guess at the end. If the clock is under three seconds, abandon comprehension and just match colors on instinct, even if you're 60% accurate. Three random taps net you about one correct on average — strictly better than one deliberate, perfect tap.