A game engine library for roguelike dungeon crawlers

Latest on Hackage:

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow to host generated Haddocks.

BSD3 licensed by Andres Loeh, Mikolaj Konarski
Maintained by Mikolaj Konarski

LambdaHack Build StatusBuild Status

LambdaHack is a Haskell game engine library for roguelike games of arbitrary theme, size and complexity. You specify the content to be procedurally generated, including game rules and AI behaviour. The library lets you compile a ready-to-play game binary, using either the supplied or a custom-made main loop. Several frontends are available (GTK is the default) and many other generic engine components are easily overridden, but the fundamental source of flexibility lies in the strict and type-safe separation of code and content and of clients (human and AI-controlled) and server. Long-term goals for LambdaHack include support for multiplayer tactical squad combat, in-game content creation, auto-balancing and persistent content modification based on player behaviour.

The engine comes with a sample code for a little dungeon crawler, called LambdaHack and described in

gameplay screenshot

Other games known to use the LambdaHack library:

Note: the engine and the example game are bundled together in a single Hackage package released under the permissive BSD3 license. You are welcome to create your own games by forking and modifying the single package, but please consider eventually splitting your changes into a separate content-only package that depends on the upstream engine library. This will help us exchange ideas and share improvements to the common codebase. Alternatively, you can already start the development in separation by cloning and rewriting Allure of the Stars or any other pure game content package and mix and merge with the example LambdaHack game rules at will. Note that the LambdaHack sample game derives from the Hack/Nethack visual and narrative tradition, while Allure of the Stars uses the more free-form Moria/Angband style (it also uses the AGPL license, and BSD3 + AGPL = AGPL, so make sure you want to liberate your code and content to such an extent).

Installation from binary archives

Pre-compiled game binaries for some platforms are available through the release page and from the Nix Packages Collection. To manually install a binary archive, make sure you have the GTK libraries suite on your system, unpack the LambdaHack archive and run the executable in the unpacked directory.

On Windows, if you don't already have GTK installed (e.g., for the GIMP picture editor) please download and run (with default settings) the GTK installer from

Screen and keyboard configuration

The game UI can be configured via a config file. A file with the default settings, the same as built into the binary, is in GameDefinition/config.ui.default. When the game is run for the first time, the file is copied to the official location, which is ~/.LambdaHack/config.ui.ini on Linux and C:\Users\<username>\AppData\Roaming\LambdaHack\config.ui.ini (or C:\Documents And Settings\user\Application Data\LambdaHack\config.ui.ini or something else altogether) on Windows.

Screen font can be changed and enlarged by editing the config file at its official location or by CTRL-right-clicking on the game window.

If you use the numeric keypad, use the NumLock key on your keyboard to toggle the game keyboard mode. With NumLock off, you walk with the numeric keys and run with SHIFT (or CONTROL) and the keys. This mode is probably the best if you use mouse for running. When you turn NumLock on, the reversed key setup enforces good playing habits by setting as the default the run command (which automatically stops at threats, keeping you safe) and requiring SHIFT (or CONTROL) for the error-prone step by step walking.

If you don't have the numeric keypad, you can use laptop keys (uk8o79jl) or you can enable the Vi keys (aka roguelike keys) in the config file.

Compilation from source

If you want to compile your own binaries from the source code, use Cabal (already a part of your OS distribution, or available within The Haskell Platform), which also takes care of all the dependencies. You also need the GTK libraries for your OS. On Linux, remember to install the -dev versions as well. On Windows follow the same steps as for Wine. On OSX, if you encounter problems, you may want to compile the GTK libraries from sources.

The latest official version of the library can be downloaded, compiled and installed automatically by Cabal from Hackage as follows

cabal update
cabal install gtk2hs-buildtools
cabal install LambdaHack --force-reinstalls

For a newer snapshot, download source from a development branch at github and run Cabal from the main directory

cabal install gtk2hs-buildtools
cabal install --force-reinstalls

For the example game, the best frontend (wrt keyboard support and colours) is the default gtk. To compile with one of the terminal frontends, use Cabal flags, e.g,

cabal install -fvty --force-reinstalls

Compatibility notes

If you are using a terminal frontend, numeric keypad may not work correctly depending on versions of the libraries, terminfo and terminal emulators. The curses frontend is not fully supported due to the limitations of the curses library. With the vty frontend started in an xterm, CTRL-keypad keys for running seem to work OK, but on rxvt they do not. The commands that require pressing CTRL and SHIFT together won't work either, but fortunately they are not crucial to gameplay. For movement, laptop (uk8o79jl) and Vi keys (hjklyubn, if enabled in config.ui.ini) should work everywhere. GTK works fine, too, both with numeric keypad and with mouse.

Testing and debugging

The Makefile contains many sample test commands. Numerous tests that use the screensaver game modes (AI vs. AI) and the dumb stdout frontend are gathered in make test. Of these, travis runs test-travis-* on each push to the repo. Test commands with prefix frontend start AI vs. AI games with the standard, user-friendly gtk frontend.

Run LambdaHack --help to see a brief description of all debug options. Of these, --sniffIn and --sniffOut are very useful (though verbose and initially cryptic), for monitoring the traffic between clients and the server. Some options in the config file may prove useful too, though they mostly overlap with commandline options (and will be totally merged at some point).

You can use HPC with the game as follows (details vary according to HPC version). A quick manual playing session after the automated tests would be in order, as well, since the tests don't touch the topmost UI layer.

cabal clean
cabal install --enable-coverage
make test
hpc report --hpcdir=dist/hpc/dyn/mix/LambdaHack --hpcdir=dist/hpc/dyn/mix/LambdaHack-xxx/ LambdaHack
hpc markup --hpcdir=dist/hpc/dyn/mix/LambdaHack --hpcdir=dist/hpc/dyn/mix/LambdaHack-xxx/ LambdaHack

Note that debug option --stopAfter is required to cleanly terminate any automated test. This is needed to gather any HPC info, because HPC requires a clean exit to save data files.

Further information

For more information, visit the wiki and see, CREDITS and LICENSE.

Have fun!


v0.5.0.0, aka 'Halfway through space'

  • let AI put excess items in shared stash and use them out of shared stash
  • let UI multiple items pickup routine put items that don't fit into equipment into shared stash, if possible, not into inventory pack
  • re-enable the ability to hear close, invisible foes
  • add a few more AI and autonomous henchmen tactics (CTRL-T)
  • keep difficulty setting over session restart
  • change some game start keybindings
  • replace the Duel game mode with the Raid game mode
  • various bugfixes, minor improvements and balancing

v0.4.101.0, aka 'Officially fun'

  • the game is now officially fun to play
  • introduce unique boss monsters and unique artifact items
  • add animals that heal the player
  • let AI gang up, attempt stealth and react to player aggressiveness
  • spawn actors fast and close to the enemy
  • spawn actors less and less often on a given level, but with growing depth
  • prefer weapons with effects, if recharged
  • make the bracing melee bonus additive, not multiplicative
  • let explosions buffet actors around
  • make braced actors immune to translocation effects
  • use mouse for movement, actor selection, aiming
  • don't run straight with selected actors, but go-to cross-hair with them
  • speed up default frame rate, slow down projectiles visually
  • rework item manipulation UI
  • you can pick up many items at once and it costs only one turn
  • allow actors to apply and project from the shared stash
  • reverse messages shown in player diary
  • display actor organs and stats
  • split highscore tables wrt game modes
  • move score calculation formula to content
  • don't keep the default/example config file commented out; was misleading
  • I was naughty again and changed v0.5.0.0 of LambdaHack content API slightly one last time

v0.4.100.0, aka 'The last thaw'

  • unexpectedly thaw and freeze again v0.5.0.0 of LambdaHack content API
  • unexpectedly implement timeouts and temporary effects easily without FRP
  • make a couple of skill levels meaningful and tweak skills of some actors
  • make AI prefer exploration of easier levels
  • permit overfull HP and Calm
  • let non-projectile actors block view
  • make colorful characters bold (if it resizes your fonts, turn off via colorIsBold = False in config file or --noColorIsBold on commandline)
  • start the game with a screensaver safari mode
  • add i386 Linux and Windows compilation targets to Makefile

v0.4.99.0, aka 'Player escapes'

  • balance the example game content a bit (campaign still unbalanced)
  • various code and documentation tweaks and fixes
  • add cabal flag expose_internal that reveals internal library operations
  • merge FactionKind into ModeKind and rework completely the semantics
  • compatibility tweaks for Nixpkgs
  • define AI tactics, expose them to UI and add one more: follow-the-leader
  • share leader target between the UI and AI client of each faction
  • specify monster spawn rate per-cave
  • extend content validation and make it more user friendly
  • freeze v0.5.0.0 of LambdaHack content API

v0.2.14, aka 'Out of balance'

  • tons of new (unbalanced) content, content fields, effects and descriptions
  • add a simple cabal test in addition to make-test and travis-test
  • generate items and actors according to their rarities at various depths
  • redo weapon choice, combat bonuses and introduce armor
  • introduce skill levels for abilities (boolean for now, WIP)
  • remove regeneration, re-add through periodically activating items
  • ensure passable areas of randomly filled caves are well connected
  • make secondary factions leaderless
  • auto-tweak digital line epsilon to let projectiles evade obstacles
  • add shrapnel (explosions) and organs (body parts)
  • express actor kinds as item kinds (their trunk)
  • add dynamic lights through items, actors, projectiles
  • fix and improve item kind and item stats identification
  • make aspects additive from all equipment and organ items
  • split item effects into aspects, effects and item features
  • rework AI and structure it according to the Ability type
  • define Num instance for Dice to make writing it in content easier
  • remove the shared screen multiplayer mode and all support code, for now
  • rename all modules and nearly all other code entities
  • check and consume HP when calling friends and Calm when summoning
  • determine sight radius from items and cap it at current Calm/5
  • introduce Calm; use to hear nearby enemies and limit item abuse before death
  • let AI actors manage items and share them with party members
  • completely revamp item manipulation UI
  • add a command to cede control to AI
  • separate actor inventory, 10-item actor equipment and shared party stash
  • vi movement keys (hjklyubn) are now disabled by default
  • new movement keyset: laptop movement keys (uk8o79jl)


  • improve and simplify dungeon generation
  • simplify running and permit multi-actor runs
  • let items explode and generate shrapnel projectiles
  • add game difficulty setting (initial HP scaling right now)
  • allow recording, playing back and looping commands
  • implement pathfinding via per-actor BFS over the whole level
  • extend setting targets for actors in UI tremendously
  • implement autoexplore, go-to-target, etc., as macros
  • let AI use pathfinding, switch leaders, pick levels to swarm to
  • force level/leader changes on spawners (even when played by humans)
  • extend and redesign UI bottom status lines
  • get rid of CPS style monads, aborts and WriterT
  • benchmark and optimize the code, in particular using Data.Vector
  • split off and use the external library assert-failure
  • simplify config files and limit the number of external dependencies


  • screensaver game modes (AI vs AI)
  • improved AI (can now climbs stairs, etc.)
  • multiple, multi-floor staircases
  • multiple savefiles
  • configurable framerate and combat animations


  • cooperative and competitive multiplayer (shared-screen only in this version)
  • overhauled searching
  • rewritten engine code to have a single server that sends restricted game state updates to many fat clients, while a thin frontend layer multiplexes visuals from a subset of the clients


  • this is a minor release, primarily intended to fix the broken haddock documentation on Hackage
  • changes since 0.2.6 are mostly unrelated to gameplay:
    • strictly typed config files split into UI and rules
    • a switch from Text to String throughout the codebase
    • use of the external library miniutter for English sentence generation


  • the Main Menu
  • improved and configurable mode of squad combat


  • missiles flying for three turns (by an old kosmikus' idea)
  • visual feedback for targeting
  • animations of combat and individual monster moves


  • the LambdaHack engine becomes a Haskell library
  • the LambdaHack game depends on the engine library
comments powered byDisqus