The Jak trilogy (Jak and Daxter: The Precursor Legacy, Jak II, and Jak 3) by Naughty Dog chronicles the life and struggle of Jak to save his world from one disaster after another. Jak has battled a dark sage drunk on his own power who is set on reforming the world, a crooked Baron allying himself with the savage Metalheads just to stay in power, the Metalheads who hate Jak and his race for no discernable reason, Errol, the Baron's right-hand man who hates Jak for permanently disfiguring him, and the Dark Makers who exist only to destroy that which the Precursors have created. Jak has his buddy, Daxter, guns, and vehicles, but his greatest asset is eco, the substance used by the Precursors to create worlds. This substance can give Jak special abilities which are very useful for completing challenges, defeating enemies, and fulfilling his destiny.
There are six types of eco, and each has a different effect on Jak depending on the game in which it appears.
- Jak and Daxter: The Precursor Legacy
Green Eco:
Green eco has two uses. When either 50 small units or one large unit of green eco are collected, Jak regains one unit of health of the three available to him. Jak will be fully healed an in possession of 50 eco units if he stands on a green eco vent. This will allow him to regain a unit of health as soon as one is lost (effectively giving him four health units). While riding on the Zoomer, green eco can be used to kill plants that have been tainted by dark eco. Green eco is easily the most abundant in the game.
Blue Eco:
Blue eco also has two uses. It allows Jak to move much faster than normal making otherwise impossible jumps easy to make. Being powered up by blue eco also allows Jak to activate Precursor technology (doors, elevators, platforms, etc.).
Red eco:
Red eco makes Jak stronger. Enemies that usually take two hits to kill now take only one. Enemies that were previously invincible can be taken down when Jak is under the influence of red eco.
Yellow Eco:
Yellow eco allows Jak to take out baddies from afar. When powered up with yellow eco, Jak can shoot fireballs from his hands. Each shot is as powerful as one normal strike, but it's much easier to clear a room of enemies with yellow eco than without. There is no limit to the number of fireballs that Jak can shoot at one time as long as he has yellow eco.
Dark Eco:
Dark eco is to Jak as spikes are to Mega Man. Any time Jak touches dark eco, death is instantaneous. Daxter managed to come into contact with dark eco at the beginning of the game without dying, but it turned him into an ottsel. You don't want to be an ottsel. They don't get to wear any pants.
- Jak II
Dark Eco:
After having been injected with dark eco and tortured for two years, Jak is no longer diametrically opposed to dark eco. Collecting enough allows him to transform into his more powerful dark alter ego. he can't use any weapons while in dark mode, but they aren't necessary. Falling into dark eco pits still means instant death, but collecting and using dark eco is necessary to complete the game.
Blue and Green Eco:
Blue eco is not usable by Jak in this game, but it does make an appearance. Blue eco is what the city uses for power, and several blue eco wells can be seen at the pumping station. Green eco can also be collected during one optional side mission.
- Jak 3
Dark and Light Eco:
Dark and light eco are used to enable Jak's dark and light forms respectively. Each dark and light move takes a predetermined amount of eco. Dark and light eco is dropped by enemies and can be found at fountains throughout the game. Dark eco is far more common that light eco, and light eco powers are used primarily for puzzle solving whereas dark eco powers are more useful for combat.
- Jak X: Combat Racing
Green Eco:
Green eco has one use in Jak X, repairing damage to your poor, battered vehicle. It's important. With as often as you're certain to be hammered by missiles, mines, and Sig's Peacemaker, you'd be crazy to pass up a green eco on the race track.
Blue Eco:
Just like in Jak and Daxter: The Precursor Legacy, blue eco lets Jak move faster. There are two ways to get blue eco, driving over a glob of it or driving over a zipper. The zipper will fill your blue eco completely, but the zipper boost will automatically use about half of it. Aside from zippers, blue eco boosts are voluntary. Holding R2 will engage your eco boost.
Yellow Eco:
Collecting yellow eco gives Jak access to forward weapons. Weapons are fired with R1, and include things like homing missiles, grenades, and a machine gun. You can only have one weapon type at a time, and yellow eco is fairly plentiful so there's no reason to horde it.
Red Eco:
Collecting red eco give Jak access to rear weapons. These rear weapons serve two purposes. They can harm opponents behind you or they can act as a chaff and deflect incoming missiles. I tend to save mine for missile deflection. I'd rather keep myself safe than dmage my opponents and be left open for an attack.
Dark Eco:
Every time you successfully use a weapon, you collect some dark eco. Fill the meter, and your weapons do extra damage until your car is destroyed. It's a great reward for those racers who can balance offense and defense.