Mutamon is a procedural monster battling simulator. Creatures are generated from random genomes and then run a natural selection simulation in the background. Whenever you're not facing a wild creature the simulation continues to run in the background. You can check the stats for the genetic simulation in the menu.

Walk through different kinds of terrain (WASD/Arrows/Joystick) to encounter them.

The wiggling tree drops items once every 30 seconds.

Use traps to catch wild creatures.

Use berries to restore your creature's energy.