Numgrid is a number puzzle game, where you have to create a complete
mathematically working board.

The board consists of 7×7 squares, whereby the corners have a random given
number. Now you have to create 8 (4 vertical and 4 horizontal) equations so
that the entire board makes sense. For this purpose you have to enter numbers
from 1 to 9 and use addition, subtraction or multiplication signs were needed.
The difficulty comes from the fact that you can’t alter the corner numbers.

For example is the given top right corner the first element of the last
vertical equation. Now choose a sign. The next number is the result of the
second horizontal equation. Then choose a sign again and use the result of the
third horizontal equation to calculate the result of that particularly
vertical equation. The result here equals the given result of the bottom right
corner. And so on.

Numgrid