Idle Game

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The typical idle game with several characteristic features.

"A game which you can play when you idle, and when you don't."

— Official description for Anti-Idle: The Game

An Idle Game (also called "incremental game" or "clicker game") is a genre of game defined by the primary feature of its strategy: leaving the game running by itself for long periods of time. This is not necessarily the only way to win; some Idle Games allow and even reward active participation, but if you "win" one, whether there's an actual end or you just got a High Score, most of your gameplay was likely in the form of letting it run while you were asleep, at work, or otherwise not involved. Because active play isn't the primary strategy, sometimes the best 'move' is counter-intuitive — one that provides an immediate benefit to active play doesn't pay off as well in the long run during idle times as another one that has a less-noticeable immediate effect but is more effective during idle play.

Idle Games usually have a concept of buying upgrades that enhance your ability to gain points (whether active, idle, or both), yielding exponential gains that Pinball Scoring can't begin to describe. Upgrade units also tend to have theoretically infinite levels, but their increasing cost causes Diminishing Returns for Balance. More complicated Idle Games tend to have multiple currencies to make the purchasing decisions for upgrades more complex. Many Idle Games also have a prestige system that functions like a New Game Plus, resetting the game but providing a "prestige" currency that carries over runs to ease subsequent runs, and some take it further by having multiple levels of prestige that reset the levels below it. Some games with these features may downplay the idling gimmick by having mini-games that drive the mechanisms for scoring and/or upgrading, or just by having so many complicated upgrades that the player is constantly busy evaluating and choosing them, but if there is a concept of an escalating point total that goes up over time, it still falls under the "Idle" umbrella.

Frequently, especially on mobile platforms, the game may provide some resource that "speeds up" the process. Charging money to provide this resource or slowing down the game very early on so as to require it is, of course, utterly inconceivable to the developers.

As the genre grows, it's clear that there are several subgenres related to gameplay style as well as goals and progression. Many idle games use Genre Blending (whether they blend multiple subgenres or different gameplay genres with idle game mechanics altogether), so take these with a grain of salt.

Unfolding: Games that start very minimalistic but open a lot more as you play, with new goals and resources showing up all the time, and often there's even a story. They're unlikely to be Endless Games like others due to eventually reaching some kind of ending.
Production-Oriented: Where you have multiple buildings, each of them producing a certain amount of a singular resource. Oftentimes, there are bonuses or upgrades unlocked upon reaching a certain quality of a building. A common design challenge is trying to make sure cheaper buildings can still take part in production, which can be accomplished if, for instance, their quality provides synergy for other producers.
Combat-Oriented: The goal is battling enough monsters to advance to the next one and you have multiple sources of damage that can be upgraded with currency dropped from monsters. After reaching a certain level, the fighter can often get some kind of upgrade or bonus. Every few stages there's a boss with a time limit to ensure you don't go too far when you're not prepared. As with the production-oriented games, it may be difficult to ensure all damage-dealers actually contribute to the fight.
Polynomial Growth: Popularised by Antimatter Dimensions, these games have producer tiers, with producers 1 giving currency and higher-tier producers giving lower-tier ones. To ensure that buying lower-tier producers is still viable, an overall multiplier to the tier's production is often given with each one purchased.
Prestige Tree-likes: Games that employ a multi-level prestige system with each level providing a different resource, often on a tree just like the original. Lower nodes typically reset everything above but increase production so it's possible to progress. Upgrades for prestige tiers can allow them to claim resources without resetting higher-tiers or just automatically gain a percentage of them each second. They're also not designed to be Endless Games (you can sometimes get the option to continue, but are unlikely to go very far), partly due to the large numbers and more defined progression systems, with an endgame placed at the point you purchase all upgrades and make significant progress with them. Practically all of them use The Modding Tree engine.

Note that certain games have an idle mode (sometimes also called observation mode) that allows the player to sit back and watch the AI play the game. Examples of this would be Unreal Tournament and Europa Universalis.

Not to be confused with idol games^note.