The roguelike genre's main characteristics were originally defined by the game that gave it its name - Rogue. However as the games it inspired grew in complexity and ambition, an exact definition became increasingly hard to peg down.
The Berlin Interpretation
The 2008 International Roguelike Development Conference produced a definition of the roguelike genre called the "Berlin Interpretation". It put forth the games ADOM, Angband, Dungeon Crawl, Nethack, and Rogue as the canon of the genre, and listed a set of criteria to be used to determine to which degree a game fit within the roguelike genre.
Note that not all roguelikes necessarily adhere to all the following factors. Even the canonical roguelikes ADOM and Angband are not completely non-modal, for example. Therefore, while the Berlin Interpretation is an important part of roguelike history, it's largely considered outmoded as a prescriptive tool for defining the genre, and instead attempts to describe some of the mechanics that underpin the genre. As with any game, it's less about the presence and absence of any given mechanic, and more about how those mechanics interact with one another to inform the player's experience.
High value factors
- Random environment generation - The game world itself is randomly generated, but also items and their description/appearance are randomized for each playthrough.
- Permadeath - Players only have one life, and upon dying, players restart with all progress lost.
- Turn-based - The game does not advance in real time, and instead only reacts once the player has taken an action.
- Grid-based - The game world is divided into a uniform grid, where the player and all enemies and items occupy a single tile regardless of actual size.
- Non-modal - The game has only one gameplay mode, where every possible player action is always available.
- Complexity - In spite of having only one mode, the game provides multiple approaches to dealing with its challenges, usually through a complex system of interactions between items and/or enemies.
- Resource management - The player has limited resources, and needs to use what he finds effectively.
- Hack'n'slash - Killing numerous enemies is the dominant part of the gameplay. Enemies have few concerns beyond killing the player.
- Exploration and discovery - The world is unknown and has to be explored to discover its contents. The nature of items and equipment is similarly unknown, and has to be discovered through use or identification skills/powers.
Low value factors
- Single player character - The game is centered on and experienced through a single player character, and ends with that character's death.
- Monsters are similar to players - The player and enemies follow the same rules.
- Tactical challenge - Learning the appropriate tactics is important, and generally necessary before any significant progress can be made.
- ASCII display - Roguelikes started out with only using ASCII characters to display their worlds, and it remains a staple of the genre.
- Dungeons - Dungeons, with distinct rooms and connecting corridors, divided into separate levels.
- Numbers - The raw numbers the game uses to describe the character current condition and abilities are exposed to the player.
The roguelike genre has influenced a number of games that combine elements of roguelikes with other styles of gameplay. Diablo and its descendants were inspired in part by roguelikes and share many of their characteristics, with the main difference being that they are real time instead of turn-based. In the 2000s and 2010s, a number of well-known independent titles such as The Binding of Isaac, Spelunky, FTL and Rogue Legacy integrated roguelike elements like permadeath, randomized environments, and management of limited resources. Some developers and commentators refer to games of this type as "roguelites" or "roguelike-likes" to distinguish them from more traditional roguelikes, even though they are very much a part of the roguelike tradition.
Since the rise of more modern re-imaginings of roguelike elements, the term has frequently come under fire as being generically and rhetorically unclear and of little value to new players of the genre. As such, a few attempts have been made to coin a more descriptive (and therefore more utile) term that should replace "roguelike", foremost among them is "procedural death labyrinth," as suggested by game developer Lars Doucet. A procedural death labyrinth privileges procedural design, punitive death mechanics, and labyrinthine design that can sometimes obscure certain functions of the game for players, instead requiring that players learn more about the game as they die and start over again in a newly-generated world.