Design Air Purifier app for iPhone and iPad

This is a game that tests the players computing ability and response ability. In the game, the player needs to design an air filter to purify the polluted air. Observe the air pollution index of the air inlet at the bottom of the screen. Before the polluted air reaches the air outlet, click the filter on the right side of the screen to extend it to decrease the pollution index to exact 0. If too many filters are used, the air will be blocked. In "Hard" mode you need to count the number of filter layers on the right, then choose a multiplier so that they multiply to exactly the pollution index.