math game. Add and subtract to 20. 'Dannyboy' has to complete 5 correct exercises in each world before he gets the key to open the next door. So he can go to the next world. If there is an error, you will hear a different sound and a new exercise will be started. The errors are displayed at the end of the exercise. There are 10 worlds, so he needs 10 keys (50 correct exercises). First touch the question mark with 'Dannyboy'. Fill in results with the small arrows (top is more, bottom is less). Control with the green 'V' button on the screen. Controls can be done on a keyboard with the arrow keys. On a tablet with the arrow keys on the screen. The doors are colored in red. Step into the flying saucer at the end. (If you make more than 20 errors, you will automatically return to the home screen). Works best on tablets.