Code Match

Code Match is a perceptual-speed drill in the style of the clerical checking sections of trading-firm cognitive assessments. Each round shows a reference code of 7 to 10 letters and digits and four candidates, exactly one of which is identical. You click the match before the round timer runs out, across 30 rounds of shrinking time windows.

Every wrong option is exactly one mutation away from the reference: two neighbouring characters swapped, a lookalike substitution such as O for 0 or S for 5, a plainly changed character, or two characters swapped far apart. The harder mutation types, and mutations buried mid-string where they are slower to spot, appear more often as the rounds progress.

Standard mode decays the per-round window from 6 seconds toward 3.5 across the 30 rounds. Pressure mode starts at 5 seconds, closes toward 2 and weights the hardest mutation types in from the very first round, so it demands the rejection-scanning technique rather than careful comparison. Pressure mode is available with a premium subscription.

The round auto-advances and is recorded as a timeout. Timeouts are tracked separately from wrong clicks in your results, because hesitating and misreading are different weaknesses to train.

Encode the reference once, in chunks of three, then scan the options and reject each at its first mismatch. Re-reading the reference for every option is too slow once the window shrinks, and position-by-position comparison across all four options does not fit in a few seconds at all.