Performing almost all actions in the game, such as killing enemies, gathering collectibles, finishing missions, and more, will grant Jason experience. Once he has gained a certain amount of experience, he will “increase” in level and earn a skill point that you can use to purchase a skill from one of three different skill trees.
The three skill trees are The Heron , The Shark and The Spider , with each one specializing in a certain aspect of the game. You will be able to purchase your first skills at the end of Harvest the Jungle, and some skills will be unlocked as you progress in the story. Other skills, however, require you to complete specific actions in the game, such as collecting 5 Relics or killing 10 enemies with a mounted machine gun.