It's a pretty fun game that makes me think of 2048, and I think it would be a good educational game for children to practice their math skills. Although at first I thought it might be more satisfying to be able to do the calculations by draging the numbers with a mouse, I think using wasd can actually force me to plan a little bit and try to do the calculation with the minimum steps/shortest route to minimise the time I use, which adds an extra layer of fun to the game :D