Addition Comparing Numbers game to play Online. Compare sums on the planets is a fun educational game to do sums and compare the results, choosing the different or odd number. Three of the four sums yield the same numerical result, but one is different from the others. To move to the next planet with the rocket and take its orbit, you must choose the different number. Practice sums and compare addition results with this educational online game from Lofgames, in the space full of planets.