After experimenting with porting the original The Legend of Zelda to the Game Boy Color, Yoshiki Okamoto's Flagship team began developing three interconnected Zelda games that could be played in any order. The complexity of this system led the team to cancel one game; the remaining two were adapted into Oracle of Seasons and Oracle of Ages. The two games, released simultaneously, interact via a Game Link Cable and a password system.
In Seasons, the Triforce transports Link to the land of Holodrum, where he witnesses the kidnapping of Din, the Oracle of Seasons, by Onox. In Ages, the Triforce transports Link to Labrynna, where Nayru is kidnapped by Veran. The main plot is revealed once the player completes both games. The player controls Link from an overhead perspective, using basic controls copied from The Legend of Zelda: Link's Awakening for the Game Boy. Link is armed with a sword and shield as well as a variety of secondary weapons and items for battling enemies and solving puzzles. The central items of the games are the Rod of Seasons, which manipulates the seasons of Holodrum, and the Harp of Ages, which allows Link to travel through time in Labrynna. Link gathers the eight Essences of Nature and the eight Essences of Time, hidden in dungeons and guarded by bosses, to obtain the power to penetrate Onox's castle and Veran's tower.
Din's attendant, Impa, tells Link that they were headed for Hyrule; she instructs him to see the Maku Tree in Horon Village, the capital of Holodrum. Link finds a sword in a cave and makes his way to the tree. The Maku Tree tells Link he will need the eight Essences of Nature and gives him the Gnarled Key, which unlocks the dungeon holding the first Essence. Link retrieves the eight Essences, hidden in eight dungeons throughout Holodrum and Subrosia, and brings them to the Maku Tree. The Maku Tree uses them to create a Huge Maku Seed, a sacred seed that cleanses evil, which allows Link to enter Onox's castle. Link enters the castle and defeats Onox. He rescues Din, who tells him that he is now a true hero and must face a new trial soon. Twinrova, watching the scene remotely, states that the Flame of Destruction has been powered by the havoc Onox has wrought.
As with Seasons, the Triforce calls out to Link. Link is transported to a forest in the land of Labrynna, where he hears screaming. In a clearing, Link finds a woman encircled by monsters. When the monsters see Link, they scatter in all directions. The woman is Princess Zelda's nurse, Impa, who asks Link to help her find a singer in the forest. Continuing through the forest, the two find Nayru, a young woman with blue hair singing on a tree stump, surrounded by forest creatures. A shadow emerges from Impa and reveals itself as Veran, Sorceress of Shadows. Veran soars into Nayru's body and possesses her. Nayru was the Oracle of Ages; her abduction causes a disruption in the time flow of Labrynna.
Link receives a sword from Impa and makes his way to the Maku Tree in Labrynna City, the capital of Labrynna. The Maku Tree is transported to the past by Veran; Link uses a time hole to travel to the past as well. The Maku Tree tells Link he will need the eight Essences of Time to defeat Veran. Link sets out to retrieve the eight Essences, hidden in eight dungeons throughout Labrynna's past and present. After getting the sixth Essence, Link is told he has the opportunity to save Nayru. He invades Queen Ambi's castle and removes Veran's spirit from Nayru, but Veran then possesses Queen Ambi. Link gathers the remaining Essences and brings them to the Maku Tree, who uses them to create a Huge Maku Seed that allows Link to enter Veran's Black Tower. Link ascends the tower and defeats Veran. He rescues Queen Ambi, and Nayru tells him that all has returned to normal. Twinrova, watching the scene remotely, states that Veran has lit the Flame of Sorrow.
The gameplay of Oracle of Seasons and Ages is similar to that of The Legend of Zelda: Link's Awakening, copying basic controls, graphics, and sounds from the Game Boy title. Like most The Legend of Zelda titles, exploration and combat take place from an overhead perspective. Link uses a sword for his primary attack, complemented by secondary weapons and items. Basic items, such as bombs and a boomerang, are common to both games. Some new items are exclusive to one game, usually with a counterpart in the other, with similar uses (e.g. the slingshot in Seasons and the seed shooter in Ages both shoot seeds, while the magnetic gloves in Seasons and the switch hook in Ages are used to access otherwise unreachable areas via special targets). Unlike most Zelda titles, a sword and shield is not always equipped when the player possesses them; they can be assigned like any other item into either of two available slots. Most of each of the games is spent finding the eight Essences (Essences of Nature in Seasons and Essences of Time in Ages), each hidden in a dungeon—a large, usually underground, area containing enemies and puzzles. Each dungeon culminates with a boss that guards the Essence.
When not in a dungeon, Link explores the overworld. In Seasons, the overworld consists of Holodrum and the subterranean world of Subrosia. The two worlds are linked by several portals. In Ages, Link travels between present-day Labrynna and the past, connected by Time Holes. In either game, some areas of one world are accessible only from portals from the other and vice versa. Holodrum, Subrosia, and Labrynna contain optional side quests and upgrades for Link and his equipment. One such sidequest is ring collection; rings provide Link with various bonuses and abilities, such as improved defense. Some rings don't have any practical uses, such as those that transform Link into an enemy creature, or do not have any uses at all, such as the secret GBA rings.
In both games, there are many circumstances when a previous item can be upgraded into a more useful form. The latter three dungeons in both games will hold a more powerful version of an item received earlier in the game. Both the sword's offensive power and the shield's defensive abilities can be upgraded twice, once through passwords and again through side quests. If Link swings an enhanced sword at full health, a sword-shaped beam will escape from the sword as a ranged attack. The number of bombs and Mystical Seeds that can be held can also be increased through the same ways as the shield and sword. Roc's Feather and the Power Bracelet are special cases, as, while the two are in both games, the former can only be upgraded in Oracle of Seasons while the latter only in Oracle of Ages.
The central item of Oracle of Seasons is the Rod of Seasons. By standing on a stump and swinging the rod, Link can change the season and affect his surroundings. For example, to cross a body of water, Link can change the season to winter and walk on the ice. Changing the season to summer causes vines to flourish, which Link can use to scale cliffs. When Link obtains the rod, he initially cannot use it. Throughout the game, Link visits four towers that house the four spirits of the seasons; each tower Link visits allows him to control an additional season.
In Oracle of Ages, the central item is the Harp of Ages, which Link uses to manipulate time. Like the Rod of Seasons, it is powerless at first. Throughout the game, Link learns three tunes to play on the harp. The first activates Time Holes, the second allows Link to travel to the past from the present without a Time Hole, and the third allows Link to switch between the two time periods at any location on the map.
Upon completing either game, players receive a password that can be used to play an alternative version of the other. In this version, some characters mention passwords that can be given to characters in the first game in exchange for an item or upgrade. Then, by taking a new password back into the linked game, the item or upgrade can be transferred. Rings can be traded by this password system or randomly created by connecting two games with a Game Link Cable.
In the alternative version, plot points are changed or expanded upon to allow the game to serve as a sequel. It also features an extended ending in which Twinrova kidnaps Zelda, and lights the third Flame of Despair to revive Ganon. The player can then enter Twinrova's lair and battle Twinrova and Ganon. Upon completing the alternative game, another password is shown that gives the player the Victory Ring, which commemorates the defeat of Ganon.
Yoshiki Okamoto, a game director for Capcom, worked with a team to create a Zelda title, but could not agree on the direction the development should take. Okamoto wanted to remake the original Legend of Zelda for the Game Boy Color, using it as a test and moving on to a "more ambitious game" if successful. Other members of the team wanted to create an original Zelda title immediately. Dismayed by the rate at which the team had been spending money for a year without results, Okamoto recruited Capcom director Yoshifumi Yamashita to the team. He also asked Shigeru Miyamoto, the game designer at Nintendo who created the series, for help. Nintendo and Capcom began collaborating concurrently on six Game Boy Color Zelda titles: two based on previous games and four original works.
The design team immediately ran into several problems. First, Okamoto wanted to release games in quick succession, spacing sequels only four or five months apart. Because Nintendo does not work in this fashion and Miyamoto was involved with other projects, the team asked Flagship, a design studio headed by Okamoto and funded by Nintendo, Sega, and Capcom, to develop scenarios for the games. This is in sharp contrast to Miyamoto's usual strategy of creating a game's plot and setting only after the gameplay has been defined. As a result, Flagship had to constantly rework the scenario and maps to match the changing gameplay. The Game Boy Color's screen presented additional problems when attempting to rework existing Zelda titles. Since the Game Boy Color's screen is narrower than that of a television, players could not view an entire room without scrolling; this made it easy for the player to overlook stairways or clues on walls.
Despite these problems, the team's experience porting the original The Legend of Zelda to the Game Boy Color emboldened them to work on a series of three games. This trilogy was referred to as the "Triforce Series", named after a fictional holy relic known as the Triforce that plays a major role in many Zelda titles. The Triforce is composed of three parts: the Triforces of Power, Wisdom, and Courage; each game in the trilogy was to be associated with one of the Triforces.
The first game of the three was demonstrated at Nintendo's SpaceWorld trade show in 1999 under the working title The Legend of Zelda: The Acorn of the Mystery Tree: Tale of Power. This action-oriented game concerned Ganon's theft of Princess Zelda and the "Rod of the Seasons", which threw the seasons of Hyrule into chaos—a clear precursor to the plot of Oracle of Seasons. In the playable demonstration, Link solved puzzles by using the Rod of the Seasons to manipulate the environment and change the current season. Tale of Wisdom, which focused on color-based puzzles, and Tale of Courage, which used times of day to solve puzzles in a mechanic similar to the use of seasons, were not shown. The Japanese title of the series was later changed to The Legend of Zelda: The Mysterious Acorn: Chapter of Power, Chapter of Wisdom, and Chapter of Courage. In the US, the games became The Legend of Zelda: Mystical Seed of Power, Mystical Seed of Wisdom, and Mystical Seed of Courage.
The games interacted with each other: players could begin with any of the three titles and have the actions of the first game affect the story of the other two. The developers considered using a cell phone adapter to transfer data, but later decided on a password system. The limitations of this system and the difficulty of coordinating three games proved too complicated, so the team scaled back to two titles at Miyamoto's suggestion. Condensing the games into a single cartridge was never considered, as the prospect of multiple endings and the added replay value afforded by the ability to play the titles in either order was very attractive. Oracle of Seasons (Chapter of Earth in Japan) was adapted from Mystical Seed of Power, Oracle of Ages (Chapter of Time and Space in Japan) was adapted from Mystical Seed of Wisdom, and Mystical Seed of Courage was canceled. Staggered releases were abandoned in favor of releasing the two games simultaneously. This made it easier for the team to test the interaction between the games and keep the style consistent. The audio for the games was composed by Pure Sound, Inc.
These sweeping design changes pushed the release dates closer to the upcoming release of the Game Boy Advance (GBA), the next system in the Game Boy line that is backward compatible with Game Boy Color games. The team considered adding special functionality to the game triggered only when played on a GBA, but was afraid that the additional development time required for the addition would cause the games to be released after the GBA. When the release date of the GBA was postponed, the team was able to incorporate GBA functionality and still release the games approximately a month before the GBA was released.
Oracle of Seasons and Ages were critical and commercial successes, selling nearly 4 million copies each. Reviews were generally positive: Chris Carle of IGN said that Seasons and Ages were "the best games ever made for the Game Boy Color", and Craig Majaski of Gaming Age called them "the two best games ever to grace a handheld system". It was rated the 34th (Seasons) and 39th (Ages) best games made on a Nintendo System in Nintendo Power's Top 200 Games list. The interconnection was seen as one of the highlight features of the titles. The ability to play the games in reverse order after completion increases the replay value, as does trading passwords between the two.
Critics enjoyed the graphics; GamePro called Seasons "bright and colorful" with "surprisingly expressive and well-designed" animations, and Gaming Target said Ages is "beautiful and creative", with "meticulous attention to detail". Gaming Age called both games "the pinnacle of good graphics on the Game Boy Color system". Although the two share graphics to a large extent, Seasons is distinguished by swapping the color palette to reflect the current season. IGN felt that the expressive colors used for the changing seasons made Seasons the more graphically impressive of the two.
Reviews of the audio were mixed. Reviewers noted that the sound was hampered by the poor quality of the Game Boy Color's speakers, although it fared favorably compared with other games for the system. The selection of songs was praised for complementing familiar Zelda songs and sounds with new music. The Zelda theme and the traditional sound effect played upon solving a puzzle were considered welcome additions, but other sound effects were criticized as simplistic "beeps".