Everyone on this website defends the same Earth. Arrow keys look around; type a comet's answer and press Enter to destroy it.

Comets appear continuously at random intervals from all directions. Each travels at its own speed; questions grow larger as they approach. Only addition and subtraction appear, with operands and answers up to two digits.

Top of the radar is your viewing direction. Each answer clears one matching comet, prioritizing the one nearest Earth. A wrong answer spends ammunition.