It’s mathematical game which move your gray cells. Invite a friend and have a great time - which of you better perform mathematical operations? Try yourself, fight for first place! Sharp mind will help you in performing a calculation. Don't be discouraged if you're not a master in this field - it's also a good way to little exercise in good company. Who turns out better in the 2 player puzzle game? You or your best friend? Spend more time on activities that will allow you a bit to learn.