Just answer each question coming at you. Answer the question to destroy the meteors before they get past you and hit earth! Don't let the health reach zero or game over. Every 5 questions the times tables get harder so hold out until times tables for 12. Meteors also get faster the harder it gets.
For some reason, the game works perfectly at times but glitches a lot at others. I am pretty sure it is just scratch in general because I have run through the entire thing for bugs.