ZeroSum

ZeroSum puzzle is played on a square grid filled with numbers and +- signs. The objective of this game is to make a given sum of numbers by navigating through a grid of numbers and associated +- signs.
Rules of this game are:
Cells are filled with numbers 1 to 5 for a 9x9 grid, 1 to 4 for a 7x7 grid, and 1 to 3 for a 5x5 grid
One cell is designated as a clue cell, you must use this cell in your solution
Start from the bottom row of the grid and move UP, LEFT or RIGHT only ending at the first row
As you move from a number cell to another, apply + or - in between; the sum of numbers is calculated as you move up, left or right
You must have a sum of zero when you reach row 1
There are no duplicate numbers in a row or a column
There is only one unique solution for a puzzle
Use 5x5 grid for young children and 9x9 for experts with a lots of visual thinking.
By now you should have download the game and play it...