A mysterious gaseous or liquid material called "Eco" exists throughout the world. Eco, which comes in numerous varieties identified by color, can have various effects. Green Eco can provide health benefits, Blue Eco gives an energy surge giving faster movements and the ability to interact with precursor technology, Red Eco increases one's strength, and yellow Eco allows the player to shoot fireballs. There is also Dark Eco which is extremely dangerous, harming most of those who touch it, and can have significant effects due to long contact, as it had on Daxter, changing him from human-elfen being into an "ottsel" (a cross between an otter and a weasel) after he was accidentally knocked into the pool by Jak. There is also White Eco, apparently a combination of the colored Echos, and of which little is known in the first game until Jak uses it in the final scene. It is not seen again until the third game, when it is used to power Light Jak in the same way as Dark Eco powers Dark Jak.
The Jak series is primarily a platformer, requiring the player to control Jak or Daxter in jumping puzzles to reach a final goal while avoiding enemy attacks. The controlled character can only take a few hits before he is down, though health can be recovered using Green Eco. Both characters can double-jump to cross large gaps or reach higher platforms. Jak can perform several melee attacks in combination with his jumping skills, many parts of the games also contain shooting and driving.
Jak and Daxter holds many similarities to platform games such as Ratchet & Clank, Sly Cooper and Crash Bandicoot. This is true in not only the similar styles of gameplay, but in that the ongoing objective is to complete specified tasks and collect items. The game is different, however, by way of the openness and flow of the game world and its common mechanic of utilizing Eco, a substance which has various uses in both gameplay and story. Here, the completed goals give Power Cells as a reward upon completion, which are needed to progress to new areas in the game world. If 100 out of 101 are collected, an alternate, canonical ending is given. Other gameplay centers around melee combats performed by Jak along with the piloting of a cycle-like hover vehicle known as a zoomer.
The game received generally positive reviews from critics and fans.
Jak II makes a radical departure from the first game in both tone and gameplay. The environment of Haven City has a grittier, run-down tone that differs dramatically from the colorful areas of the first game, and the characters are generally more hostile, using slightly more mature language. As for gameplay, more melee combos have been added in addition to multiple firearm weaponry that can be upgraded into new type of firearms after acquiring the specified weapon mod upgrade. Combos and firing techniques are integrated, and though Eco is no longer the dominant character booster, Jak now exhibits a transformation known as Dark Jak that comes with a range of powerful moves as well as a gauge for when it can be activated. Since Haven City is so large, more options for vehicles which the player can "high-jak" is available to make traveling across the vast metropolis more efficient. The vehicles are capable of hovering at a high altitude or low altitude and come in a variety of styles, with the most bulky car-like ones being more fortified against enemy fire, though slightly slower, and the smaller cycle-like ones lacking armor but are significantly faster. A hover board is also obtainable some time later which allows the player to maneuver effortlessly over dangerous grounds and large areas at a considerable speed and comes with the ability of performing tricks.
This game marks the beginning of tournament vehicle racing against other characters operated by the CPU, which becomes a tradition in the later installments as well as the major gameplay in the spin-off Jak X: Combat Racing. The use of accelerator rings returns in bonus missions and a one-on-one between Jak and KG Commander Erol throughout various parts of Haven City. Selectable boosters are available during track racing with all racing, on and off track, being conducted on advanced modernized zoomers.
As Jak and Daxter work to fulfill the life debt they owe to the city and Damas, they learn that the planet's end is coming, from a harbinger of destruction known as the Day Star. The answer to this impending danger is a planetary defense system, which lies deep in a place known as the Catacombs. As Jak and Daxter work to find their way to this place, so too does Count Veger, who is taking dangerous steps to find the Precursors there and receive great power so that he may live out his fanatical dream of becoming a hero of the universe. When Jak and Daxter make their way back to Haven City, it falls on their shoulders to destroy the Metal Heads and the KG, make their way to the Catacombs before Veger and save the world from the Day Star.
In this installment, Jak's attitude to being the hero is once again challenged, with him, at first, holding a grudge against the city for having turned on him, leaving him for dead in the Wastelands. But despite his personal feelings, he chooses to help his friends at least and in doing so learns about himself and the power within him. More of Jak's destiny is revealed including the secrets behind the world's hero Mar, the true nature of the Prescursors, and the threat the Precursors' enemies- the Dark Makers- pose on the planet with their nearing airship, the Day Star.
The gameplay in this game features an upgrade from Jak 2, with even more weapon modifications and combos to perform, along with Jak gaining a new transformation called Light Jak. Light Jak acts primarily as a defensive and healing transformation that is later capable of flight, whereas Dark Jak retains its savage nature with deadly offensive capabilities, both being operated by their individual gauges respectively. Though the hover vehicles are still available in Haven City, much of the city has been destroyed due to the war and thus there is much less traffic as in the previous game. Multiple types of land vehicles become unlockable in Spargus, each with their own unique type of weaponry, and are used to journey across the vast desert expanse for various missions. The hover board is once again available and comes with a few new tricks to perform as well as "stunner" waves that come in handy when dealing with the smaller Metal Heads. Daxter also becomes playable at certain points to solve puzzles and clear routes for Jak to follow.
Racing makes another comeback as in the previous installment, except that land vehicles in Spargus are the primary function for all competitions. The Race Dome at Haven City is almost completely destroyed and so the only zoomer races are done by bonus missions through accelerator rings, while in Spargus accelerator ring-type races are conducted on the backs of animals called Leapers (which also serves as extra modes of transportation throughout the Wasteland city). A new type race-mode mini-game is also available that is playable only with Daxter that involves him riding on a rocket around the harbor section of Haven City.
As you play, a 'friendly' man Razor keeps on threatening Jak and Daxter that Mizo and his 'dream' team would kill them. Eventually he goes out of retirement just "for you, Jak" and joins forces with Mizo's group to race. Later in the game, old faces return to aid/damage Jak's team for different reasons. Sig, the new king of Spargus after Damas' demise, comes to help his unlucky friends out on the track, despite he (ironically) missed the meeting that would have poisoned him because of his reigning duties; and Kleiver, a demanding and shallow Wastelander who wants to even the score between him and Jak which settled during the events of Jak 3 (whether Jak liked it or not). Pecker also makes a reappearance, but as a partnered commentator alongside G.T. Blitz, much to Daxter's dislike, and relays information he hears about the bets of the races to Jak's team in an effort of assistance.
After Jak's car was sabotaged in a race, Keira and the others find out that they were the same weapons used to kill G.T. Blitz's own father. They tell Blitz about this, but remain surprised that Blitz wasn't in the least bothered about both the tight situation and the participants safety. Later on, an important call comes in from the crime lord Mizo, telling them to back off from the race while they still had the chance. Since none from Jak's team had a choice to participate the championship race in the first place (with the exception of Sig), Jak declines the 'offer' in his team's name. Near the very end of the game G.T. Blitz states that a new unknown driver is on the track for the final race. Almost immediately it is known that the 'phantomatic' driver is no other than Blitz himself.
After Jak and co. finally win the final race, thus achieving the antidotes for the poison and winning the Kras City World Championship race for jigs, G.T Blitz snaps. Blitz reveals to over 2 million spectators (unknowingly to him) that he was the infamous crime lord Mizo himself, then proceeds by stealing the antidotes and dashes away from the race. Jak then hunts him down in order to retrieve the vaccines needed for him and his friends to live. After retrieving said antidotes, Mizo was literally left to be blown up in his wrecked car. During the victory celebration, when everyone has been cleared of the poison, Rayn congratulates them and leaves Krew's will behind her. It reveals that she knew about the poison all along and that she manipulated them in her father's fashion, her never actually being poisoned to begin with. Rayn is then shown driving off ordering for all the other major crime lords to gather together since she now ruled Kras City among ordering for her friends to be left alone. Despite the clear betrayal, none seem to be too fazed by it and all continued the celebration. During the final scene, Jak and Keira finally kiss.
The gameplay is centered completely around racing in customizable land vehicles that are capable of having purchased or prize upgrades. There are three basic types of vehicles per tournament: speed, agility, and armored; with several of each being available as the game progresses while others must be unlocked. Multiple parts of the cars can be modified, including the color scheme, to give the vehicle a unique look that may or may not have an effect on the driving experience.
The Power Cells and various types of Eco make a comeback (as in Jak 2 only Dark Eco and Green Eco were prominent, with the addition to Light Eco in Jak 3). The Power Cells and other Precursor artifacts are used in specialized mission races as either objects to hunt for or as unique weaponry in which the booster charges and fires at whomever is ahead of the player.
The Eco's are obtainable simply by driving through them. Green Eco replenishes health lost when the car is damaged, Yellow Eco is used as a frontal offensive mechanism (which ranges in a variety of weaponry from Machine Gun rounds to Rockets and Energy Blasts to eliminate those in front of the player), while Red Eco is a defensive mechanism that also features in attacking from behind (ranging from creating a shield around the car to having a turret hover above to shoot all at close range and leaving behind highway dangers such as Oil Slicks, Smog, and Land Mines). Blue Eco is an exceptional piece as it runs on a gauge that can be filled either by collecting said Eco or charging it by powersliding around tight curves on the track, which allows for the player to give their vehicle a tremendous speed boost until the gauge runs out. The Eco powerups have to be used in order to make room to obtain new ones, each of which are random.
The game's storymode is centered around the Kras City Championship that is split into 4 tournaments, each with a colored Eco Grand Prix. The player must win first place in each of the lesser races before moving on to the Grand Prix races where the system is 2 out of 3. Afterward, the next tournament becomes available with the 4th tournament acting as the last in the Grand Championship.
Multi-player mode is available with a large cast of selectable characters, some of which aren't available to play as in storymode, and a scene selector is also available for purchase (as it is with Jak 2 and Jak 3) with bonus materials added.
A bonus disc given out by Sony Computer Entertainment in a special promotion, the Complete Trilogy Movie DVD gives gamers a recap of the Jak & Daxter series with a run of scenes from the game franchise. The 90 minute movie is about the exploits of Jak and his infamous sidekick Daxter, who also provides the cinematic narration. There is also a behind-the-scenes look at Jak X: Combat Racing and its fully playable demo, developer interviews and footage of Daxter's game on the PSP. Although the title would indicate that it is a DVD video playable on any DVD player, the disc is only playable on PlayStation 2 or 3 consoles due to the demo of Jak X. In Europe the Trilogy Movie was released as a bonus with Jak X. Unlike in the US it is playable on any DVD player.