read the updat on last sene (GAMEPLAY NOTE: The game does not freeze in the last scene. After the monster arrives, click the arrow shaped plant next to the frog.)
upgrade only wen u need it lik upgrade heet resistance wen theres a drot dnt uprgrade any of the symptomsthell close almost every thing witch stops ur disease from spreading do tht last
and dnt jus upgradethings tht kill upgrade both