When a card is tapped, the card is reversed and "=" symbol appears. When tapped again, turned to the front side.
With one "=" symbol, make the both side of "=" same value.
You can select a game mode from "Selected 100 questions" and "Random questions" mode.
On "Selected 100 questions" mode, you can get cards or mats with new design. You can start from a question you are challenging, also able to start from a question you've solved.
On "Random questions" mode, questions are made at random.
With triple-line button at a right-top of the title screen, you can see a rule in detail. Also, you can configure a design of cards and mats, and sound effect and BGM.