In the fish tank game the goal is to keep the fishes alive. This is done by controlling the temperature, salinity, level and particle density of the tank. If the "fish happiness" indicator drops below 70 percent the fishes will die.
There are three different modes:
Manual mode - Control all parameters of the tank manually.
PID mode - Tune the PID controllers.
Game mode - Keep the fish alive for 35 seconds during all sorts of equipement malfunction.