Digits from 1–9 play one at a time. For each new digit, answer with the result of it and the digit right before it - by default the sum, so hearing "3" then "5" means you type 8.

Answer as soon as you know it - type it, or tap it on the answer buttons with the on-screen keypad; there's no submit step, it's checked instantly. Answer correctly several times in a row and the pace speeds up; miss a few in a row and it slows back down.

CCT's core mechanics (the adaptive-interval PASAT rule) are adapted from CCT by tim22dev22 (MIT) - see Credits.