The three games

Read out loud

A Roman numeral appears: MCMXLV. You say “one thousand nine hundred forty-five”. On a large number, the app listens to the whole utterance before judging: a hesitation in the middle — “one thousand… nine hundred forty-five” — is not a mistake, it is an answer being built.

Write by choosing

A number appears — 400 — and four spellings are offered, hiding the classic mistakes: CDD, CD, DC, CCCC. You tap the right one. Choosing makes you recognise the form: it is the discovery stage, and the best way to flush out the traps — IIII for IV, VI for IV, XXXX for XL, DDC for DC.

Write on the Roman keypad

A number appears, and you build it with the seven keys I V X L C D M, then confirm. Building it forces you to produce the form without seeing it: that is what anchors the rule. One key too many can be erased before confirming.

The move from choosing to the keypad is gradual. From I to X, you choose among four. From XI to C, choosing and the keypad alternate. Beyond that, the keypad alone: four spellings of MCMXLV could no longer be told apart.