Tree of roguelike evolution

In some cases, it may be clear that one roguelike derives from another. For example, NetHack was built atop Hack, so its lineage seems clear. Other times, determining relations proves more difficult. Where does ADOM fit? It appears to be a hacklike, but does not share its codebase with any other game. Similarly, Avanor adopts the gameplay, but not the actual code, of ADOM.

                 Rogue                                                           DND
       ____________|_____________                                                 |
      |     |      |             |                                                |
    Moria  Larn  Omega         Hack                                               |
      |            |             |                                                |
   Angband         |          NetHack                                             |
   ___|___         |   __________|__________                                      |
  |       |        |  |    |        |       |                                     |
ToME  ZAngband     ADOM  ZapM   SLASH'EM  Crawl                                  ADND


Schematic family tree of popular roguelike games, showing inheritance by play style.

Forming a series of differentiators might offer a standard nomenclature for describing roguelikes from which one might construct taxonomic groups of roguelikes.

List of differentiators:

• Plot vs. Plotless: a plot-based roguelike sports a non-trivial plot. Note that quests ("kill the bad guy at the bottom", etc.) don't make a non-trivial plot. Plot-based roguelikes would include ADOM, GearHead or LambdaRogue.
• Dungeon persistence: persistent dungeons impact gameplay in many ways. They lead to finite in-game resources countered by unlimitted storage capacity (assuming object persistence, as well). They also leave few alternatives to confronting difficult obstacles and foes. Pacing thus differs radically, and this becomes a significant differentiator. ADOM, despite the infinite dungeon, would fall into this camp. Bands are almost uniformly non-persistent.
• Equipment upgrade path: how likely are you to finalize a piece of equipment early in your game? Bands tend to have a deep upgrade cycle, where a large portion of the game lies in choosing when and how to upgrade. Hacklikes tend to have a trivial equipment upgrade, where the difficulty lies in acquiring equipment rather than in deciding whether to use it.
• Inventory size: a relatively wide spectrum is present here. Bands often have fixed inventory slots that make this an important part of the game. However, NetHack also has limited inventory — 52 slots or so, until one acquires a bag. Even with a bag, items stored therein are not within ready reach. ADOM, by contrast, allows one to cart along pages of inventory provided one has the strength of Atlas.
• Dungeon size: do dungeon levels fit on one screen? Most bands make levels that do not fit on a screen. Hacklikes tend to fit on one screen. Note that Crawl represents an exception to this. There are important gameplay differences when one can see the entire dungeon at the same time. Consider the effect on "Detect Monster"-like spells. (While ADOM resizes to fit the screen, note that it will always fit the screen!)
• Wilderness: is there a wilderness area outside of the dungeon? ZAngband and ADOM are examples of this.
• Town with supplies: are there surface towns that carry needed adventuring supplies?

We can thus create the following adhoc categories:

• Hacklike: persistent dungeons, little equipment upgrade path, large inventory size, single screen dungeon size, no town with supplies
• Band: non-persistent dungeons, equipment upgrade path, limitted inventory size, multi screen dungeons, town with supplies.
• ADOMlike: hacklike + plot + wilderness
• ZAngbandlike:-Band + wilderness

See also the wikipedia:Roguelike article.