If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
You are on a graveyard, alone with your shotgun. Alone? Not really, suddenly math enthused zombies appear and try to
raise wisdom with your brain!
You want to stop them? Answer their math tasks to send them back to hell!
You are good in mental arithmetic? You have to be better!
Just write down numbers, negative with “-”.
Mistyped numbers? Just go on, no enter/return needed. If a grenade appears, write “grenade” to throw it, all current zombies will be gone, yeah!