All your operation needed in the gameplay is inputting any numbers. The main character head to a certain door. Along that way, other monsters approaches him and one-sidedly start a game with number. Other monsters is going to makes him an easy target. The main character has no way of explaining the game rules to you. Needed observation and consideration for inputting any advantageous number and win. Open the door with him. The latest version contains 7 levels: 5 normal levels, 1 hidden level, and 1 special level where a hidden monster is in. It takes about 2 minutes from starting the first level to reaching the door. I recommend trying the demo version before you buy. Because I hope you choose games you can really love. The "Download Demo" button is on the right part of this page. 3 normal levels only in the demo version. The save progress feature is not available in the demo version. Some enemy monsters of the demo version have different status values.