If the hand contains all four tiles of a wait it would have, that wait is not counted.

There may be invalid problems from time to time. There is no penalty for submitting an empty answer.

Hands that can score chiitoitsu and ryanpeikou are dealt with 'correctly'; all the waits count.

Use the mouse or number keys [1–9] to select an answer, then Enter to submit.

Each correct tile is rewarded with 1,000 points; each incorrect one is punished by 2,000. Merely missing correct answers is not counted as a mistake and is not punished.

That base score is then affected by time bonus and difficulty multiplier, which are as follows:

• The maximum time bonus is 25%, earnt by answering within 3 seconds.
• After that, it will decay to zero as the timer runs.
• If the time runs out, the answer will be submitted with no bonus at all.