Alien fish are invading Bikini Bottom and eating all of the plants. Only they did not realize it is Earth Day, and the plants are fighting back! The player controlling SpongeBob must shoot seeds at the alien fish. The player can move the mouse to move the cursor and left click to shoot. The player must also click on the plant to reload. The player can also shoot a jellyfish to earn even more points. In higher levels, the alien fish start moving faster.
The game ends when the player loses all of its plants or beats level 20.