Your aim is to help a little Plankton to survive for as long as you can. Use YOUR MOUSE to drag and drop in the easy mode, or use ARROW KEYS in hard mode to avoid the baddies, eat the food stuff that you find along the way and proceed further. Note that you will encounter a Boss at the end of each zone.
Help the little plankton become a completely new creature. Avoid, Eat, and Evolve!
Square Enix has launched their Dragon Quest 8 Official Community website called SlimeKnights. I'm a huge fan of the series, literally the second console game I ever played, after the original Super Mario Bros. game, was Dragon Warrior I (since you couldn't avoid playing Super Mario Bros. - it came in the Nintendo box).