Use the numbers as a hint to avoid dangerous, and find the route.
The number is dangerous or the routes (by setting) around it.

Infer the route from the arrangement of numbers and confirm it.
The row of 1 and the row of 4 are always displayed.
(It's some info that might help)

When the stage is cleared, player gets some points.
To use point to visible the invisible number.
It will help you to reasoning.

It get a higher grade title according to the remaining points when the story end.

In the Mugen-Mode, to be playable forever until the player abandoned.
Record the number of the Stage cleared, and of the hint used.