It's the year 2025, a race of super intelligent X aliens, challenges the human race's knowledge, experimental secret prototype droids are humanity's last chance of survival. The prototypes take the shots. You . . . have to call them . . .X Challenge brings an astonishing revamp to the mental math games. The only mental math workout packed with special sound and glowing visual effects.The game is straight forward; the X aliens UFO shoots math questions on the prototype droids, Zirus and Gaya. You have to control Zirus and Gaya by answering the question correctly and shooting it with the plasma beam. The faster you shoot the 100 questions, the higher you score.You are allowed three plasma cells (i.e. three errors), on the fourth error the prototype droid will be damaged.- Easy --> Question shoot out +100- Medium --> Question shoot out +200- Hard --> Question shoot out +300Features:- Easy pick up and game play- Fun for all ages- Epic robotic and future tech sound effects- Glow visual effects- Answer simply by tapping not writing- Math questions for all ages, three different difficulties- Online high scores, challenge your friends all over the world- More than 1000 math questions, answers chosen precisely to set the difficulty level- FREE updates with new questions, new prototype droids, themes and more!- Separate background music/sound effect mute buttons- Very low battery consumption, (glow effect on black background)- The best mental math workout game app and It's FREE!