Nintendo has a long history of experimenting with its franchises—sometimes unintentionally. When Nintendo of America "Game Master" Howard Philips judged Super Mario Bros. 2 too difficult for western fans, the company repurposed the simpler Yume Kojo: Doki Doki Panic by swapping out its characters for Mario and his pals. More famously, Zelda II diluted the original title's purely top-down perspective and freeform exploration by switching to a side view during combat and introducing RPG-like character progression.

For various reasons, both of those titles were retroactively categorized as side stories. In other cases, Nintendo realized early in development that a game's core concepts were unorthodox and proactively gave them the subtitle "Gaiden," Japanese for side story, specifically one connected to another work. The "Gaiden" label affords developers more freedom to experiment by communicating to Japanese players that they should expect the unexpected. Zelda Gaiden, aka Majora's Mask, is the most popular case—it remixed Ocarina of Time's characters, added a timer, and emphasized side quests over dungeons.

Fire Emblem Gaiden is another case of Nintendo preemptively categorizing a sequel as a lateral step rather than a leap forward. Published by Nintendo for the Famicom in March 1992, Fire Emblem Gaiden was both familiar and different to fans of the first game, released two years earlier. A tactical RPG, Gaiden had players maneuver units on a battlefield, take terrain such as forests and hills under consideration before attacking, wage battle according to a turn-based system, and follow an intricate storyline.

Nearly every other aspect of Fire Emblem Gaiden was either new or modified from the first game. The reason for so many dramatic changes stems from series creator and director Shouzou Kaga's desire for refinement. While the first game had been well received, Kaga, like most creative types, found it difficult to look past flaws. Gaiden was his chance to refine his ideas.

One of the first items on Kaga's to-do list for Gaiden was movement. The first game consisted of battlefields. Players moved their units character by character, like pieces on a board. For Gaiden, Kaga and his team created an overworld complete with towns and dungeons that could be freely explored.

When players bump into enemies, the perspective shifts gears into turn-based combat that plays out a battlefield made up of grids, much like the first game's topography. Most battles are won when players kill either a boss or all of the enemies in an area, rather than capturing a location such as a gate. In the first game, weapons broke down over time. Gaiden equips every unit with a default weapon that never breaks. That variation, coupled with units learning spells by leveling up instead of by equipping tones, cuts down on inventory management and lets players devote more attention to tactics.

Although Fire Emblem staples such as the weapon triangle (a paper-rock-scissors chart of strengths and weaknesses) and the Support system (bonds through which characters become friends or romantically involved and produce offspring that grow into a new generation of heroes) weren't established until later, Gaiden allows players to increase their odds of dealing critical strikes by placing protagonists Celica and Alm beside each other in battle.

Most elements in Fire Emblem Gaiden come in pairs. Celica and Alm are friends and adopted siblings. The story centers on two gods and two kingdoms at war over two ideologies that clash with one another. Even the story bifurcates. Alm and Celica end up on opposite sides of the conflict, with Alm getting deeply invested in the war while Celica investigates the disappearance of a key character.

As players came to expect as the series continued, Gaiden's story and combat inform one another. Whereas each unit started as an immutable class in the original game, Gaiden let players promote troops into different classes by visiting a shrine. For example, Alm starts out as a Fighter and strives to grow into a Hero, while Celica graduates from Priestess to Princess. Not only do promotions offer gameplay benefits, they infuse characters with a sense of progression as the story unfolds.

Like Legend of Zelda: A Link to the Past, the third entry in the Fire Emblem series shed much of Gaiden's influence and backpedaled to mechanics from the original game. Gaiden will get its chance to shine later this year when Nintendo publishes Fire Emblem Echoes: Shadows of Valentia on 3DS—a remake of the second game, and the first time it will be published outside of Japan.

Announced during a Nintendo Direct event in January, Shadows of Valentia takes place on a a from-the-ground-up reconstruction of the titular continent. Locations such as towns can still be explored, albeit from a behind-the-back perspective to show off the remake's enhanced graphics, and turn-based battles with a tactical bent dictate the flow of combat.

Other details, such as whether Shadows of Valentia will incorporate newer Fire Emblem trappings like the weapon triangle and Support, remain unknown. Barring an unforeseen disaster, Gaiden's remake should benefit from the fact that Fire Emblem is even more beloved now than in its heyday. Like progeny begat from the franchise's trademark Support system, a legion of new fans join veteran players in anxiously awaiting more character- and tactics-driven exploits.

Fire Emblem Echoes: Shadows of Valentia is slated for release on Nintendo 3DS this May. The first mobile entry in the series, Fire Emblem Heroes, is available now for iOS and Android platforms.