LambdaHack
LambdaHack is a Haskell1 game engine library for ASCII roguelike2games of arbitrary theme, size and complexity, with optionaltactical squad combat. It's packaged together with a sampledungeon crawler in a quirky fantasy setting. The sample game can betried out in the browser at http://lambdahack.github.io.
As an example of the engine's capabilities, here is a showcaseof shooting down explosive projectiles. A couple were shot down closeenough to enemies to harm them. Others exploded closer to our party membersand took out of the air the projectiles that would otherwise harm them.Actual in-game footage.
This was a semi-automatic stealthy speedrun of the escape scenarioof the sample game, native binary, SDL2 frontend, single tinybitmap font. The enemy gang has a huge numerical and equipmentsuperiority. Our team loots the area on auto-pilot until the first foeis spotted. Then they scout out enemy positions. Then hero 1 drawsenemies and unfortunately enemy fire as well, which is when he valiantlyshoots down explosives to avoid the worst damage. Then heroine 2 sneaksbehind enemy lines to reach the remaining treasure. That accomplished,the captain signals retreat and leaves for the next area (the zoo).
Using the engine
To use the engine, you need to specify the content to beprocedurally generated. You declare what the game worldis made of (entities, their relations, physics and lore)and the engine builds the world and runs it.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 (SDL2 is the defaultfor desktop and there is a JavaScript browser frontend)and many other generic engine components are easily overridden,but the fundamental source of flexibility liesin the strict and type-safe separation of code from the contentand of clients (human and AI-controlled) from the server.
Please see the changelog file for recent improvementsand the issue tracker for short-term plans. Long term goalsinclude multiplayer tactical squad combat, in-game contentcreation, auto-balancing and persistent content modificationbased on player behaviour. Contributions are welcome.Please offer feedback to mikolaj.konarski@funktory.com or, preferably,on any of the public forums.
Other games known to use the LambdaHack library:
- Allure of the Stars6, a near-future Sci-Fi game
Note: the engine and the sample game are bundled together in a singleHackage3 package released under the permissive BSD3 license.You are welcome to create your own games by forking and modifyingthe single package, but please consider eventually splitting your changesinto a separate content-heavy package that depends on the upstreamengine library. This will help us exchange ideas and share improvementsto the common codebase. Alternatively, you can already start the developmentin separation by cloning and rewriting Allure of the Stars10and mix and merge with the sample LambdaHack game rules at will.Note that the LambdaHack sample game derives from the Hack/Nethack visualand narrative tradition9, while Allure of the Stars uses the more free-formMoria/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 of the sample game from binary archives
The game runs rather slowly in the browser (fastest on Chrome) and you arelimited to the square font for all purposes, though it's scalable.Also, savefiles are prone to corruption on the browser,e.g., when it's closed while the game is still saving progress(which takes a long time). Hence, after trying out the game,you may prefer to use a native binary for your architecture, if it exists.
Pre-compiled game binaries are available through the release page11(and, for Windows, dev versions continuously from AppVeyor[18]).To use a pre-compiled binary archive, unpack it and run the executablein the unpacked directory or use program shortcuts from the installer,if available. On Linux, make sure you have the SDL2 libraries installedon your system (e.g., libsdl2-2.0-0 and libsdl2-ttf-2.0-0 on Ubuntu).For Windows (XP no longer supported), the SDL2 and all other needed librariesare included in the game's binary archive.
Screen and keyboard configuration
The game UI can be configured via a config file.The default settings, the same that are built into the binary,are on github at GameDefinition/config.ui.default.When the game is run for the first time, or whenever the settings fileis deleted, the file is written to the default user data location,which is ~/.Allure/ on Linux,C:\Users\<username>\AppData\Roaming\LambdaHack\(or C:\Documents And Settings\user\Application Data\LambdaHack\or something else altogether) on Windowsand Inspect/Application/Local Storage under RMB menuwhen run inside the Chrome browser.If the user config file is outdated or corrupted, it's automaticallymoved away together with old savefiles, which guarantees that the newdefault config file is ultimately put in its place.
Screen fonts and, consequently, window size can be changed by editingthe config file in the user data folder. The default bitmap font16x16xw.bdf used for the game map covers most national charactersin the Latin alphabet (e.g. to give custom names to player characters)and results in a game window of exactly 720p HD dimensions. The 8x8xb.fntbitmap font results in a tiny window and covers latin-1 characters only.The config file parameter allFontsScale permits further window sizeadjustments, automatically switching to the scalable 16x16xw.woffversion of the game map font. Config file option chosenFontset governsnot only the main game map font, but also the shape of the rectangular fonts,if any, in which longer texts are overlaid over the map.
For high resolution displays and/or if fullscreen mode is requestedin the configuration file, allFontsScale needs to be set.E.g., scale 3 works for 4K displays. Otherwise, the letters may betoo small or, in fullscreen or on retina displays in OS X,the screen may be automatically scaled as a whole, not each letterseparately, softening letter edges of the square fonts that shouldbe pixel-perfect and crisp.
If you don't have a numeric keypad, you can use the left-hand movementkey setup (axwdqezc) or Vi editor keys (aka roguelike keys) or mouse.If numeric keypad doesn't work, toggling the Num Lock key sometimes helps.If running with the Shift key and keypad keys doesn't work,try the Control key instead. The game is fully playable with mouse only,as well as with keyboard only, but the most efficient combinationmay be mouse for menus, go-to, inspecting the map, aiming at distantpositions and keyboard for everything else.
If you are using a terminal frontend, e.g. the best supported vty frontend,then numeric keypad (especially keypad * and /) may not work correctly,depending on versions of libraries, terminfo and terminal emulators.Toggling the Num Lock key may help or make issues worse. As a workaround,in the vty frontend, numbers are used for movement, which sadly preventsthe number keys from selecting heroes. The commands that require pressingControl and Shift together won't work either, but fortunately they arenot crucial to gameplay.
Some effort went into making the vty frontend usable with screen readers,but without feedback it's hard to say how accessible that setup is.As a side effect of screen reader support, there is no aiming linenor path in vty frontend and some of map position highlightingis performed using the terminal cursor. Screen readers may also workbetter with animations turned off, using --noAnim or the correspondingconfig file or main game menu options.
Compilation of the library and sample game from source
The recommended frontend is based on SDL2, so you need the SDL2 librariesfor your OS. On Linux, remember to install the -dev versions as well,e.g., libsdl2-dev and libsdl2-ttf-dev on Ubuntu Linux 16.04.Other frontends are compiled similarly, but compilation to JavaScriptfor the browser is more complicated and requires the ghcjs15 compilerand optionally the Google Closure Compiler16.
The latest official version of the LambdaHack library can be downloaded,compiled for SDL2 and installed automatically using the 'cabal' tool,which may already be a part of your OS distribution, but if it's too old(version 3.4 or later is required) you can download the whole currentcompilation suite as described at https://www.haskell.org/downloads/.Get the LambdaHack package from Hackage3 as follows
cabal update
cabal run LambdaHack
For a newer snapshot, clone the source code from github5and run cabal run LambdaHack from the main directory.Alternatively, if you'd like to develop in this codebase,the following speeds up the turn-around a lot
cp cabal.project.local.development cabal.project.local
and then you can compile (and recompile) with
cabal build .
and run the game with
make play
There is a built-in black and white line terminal frontend, suitablefor teletype terminals or a keyboard and a printer (but it's going to usea lot of paper, unless you disable animations with --noAnim). It is usedin CI and for some tests and benchmarks defined in Makefile. To compilewith one of the less rudimentary terminal frontends (in which case you areon your own regarding font choice and color setup and you won't havethe spiffy colorful squares outlining special positions that exist in SDL2frontend, but only crude cursor highlights), use Cabal flags, e.g,to switch to the vty console frontend optimized for screen readers, run
cabal run -fvty LambdaHack
Testing and debugging
Unit tests and integration tests can be run and displayed with
cabal test test --enable-tests --test-show-details=direct
To prepare doctests7, set tests: True in your cabal.project.local.Afterwards, doctests can be executed with
cabal build . && cabal exec cabal test doctests
and their detailed results observed in a log file.(Repeating cabal build before each testsuite run is requieddue to bug https://github.com/haskell/cabal/issues/7522.)
The Makefilecontains many sample automated play test commands.Numerous tests that use the screensaver game modes (AI vs. AI)and the teletype frontend are gathered in make test-locally.Some of these are run by CI on each push to github.Test commands with prefix frontend start AI vs. AI games withthe standard, user-friendly frontend and auto-locating the game binary.
Run LambdaHack --help to see a brief description of all debug options.Of these, the --sniff option is very useful (though verboseand initially cryptic), for displaying the traffic between clientsand the server. Some options in the config file may prove useful too,though they mostly overlap with commandline options (and will be totallymerged at some point).
Coding style
Stylish Haskell is used for slight auto-formatting at buffer save; see.stylish-haskell.yaml.As defined in the file, indentation is 2 spaces wide and screen is80-columns wide. Spaces are used, not tabs. Spurious whitespace avoided.Spaces around arithmetic operators encouraged.Generally, relax and try to stick to the style apparent in a fileyou are editing. Put big formatting changes in separate commits.
CI checks the code with hlint . using the very liberal configurationfile at .hlint.yaml. If hlint is still too naggy, feel free to addmore exceptions.
Haddocks are provided for all module headers and for all functions and typesfrom major modules, in particular for the modules that are interfacesfor a whole directory of modules. Apart of that, only very importantfunctions and types are distinguished by having a haddock.If minor ones have comments, they should not be haddocksand they are permitted to describe implementation details and be out of date.Prefer assertions instead of comments, unless too verbose.
The 'pointman' from game manual and UI is called 'leader' in the source codeand there are a few more mismatches, though the source code namingand the UI naming should each be consistent in separation.If the UI names stick, perhaps source code will be renamed at some point.
This codebase is an experiment in extensive use of states without lens.So far, it works, doesn't result in much larger files or lotsof repetition and has the added benefits that newcomers don't needto learn any lens library. Record punning, etc., definitely helps.
First steps reading the codebase
I'd start with
That's where keypresses are assigned commands, help texts and categories(including special categories indicating that a group of keypressesforms an in-game menu). This file is specific to a particular game(hence GameDefinition in the path) and the engine dynamically createsin-game help screens based on this file and on player config filethat can partially overwrite it.
The commands assigned to keypresses are interpreted by the UI client(each faction in the game uses a client and the player's client additionallyhas UI capabilities) in the following module:
By this point you've seen one of the six major command sets(HumanCmd, Effect, UpdAtomic, Request, Response, FrontReq)and one of around ten distinct interpreters for the commands(mostly in Handle* modules). You've also seen a bit of UI client code,but not the AI client nor the server (game arbiter) code.The wiki17 contains not entirely outdated further reading aboutthe client-server architecture.
At this point, before trying to grasp anything more and drown in abstraction,you are welcome to pick up a few good first issue-labeled ticketsand get hands-on experience with the codebase.
For further study, note that most of the commands are interpreted in monads.Server and clients share some of the customized monadic API, but theirmonads are implemented differently (in *Implementation modules).All these monads are state monads (keeping various aspects of game state),therefore the semantics of a command is a state transformer with extraside effects (e.g., frontend drawing is such a side effect).
The "main loop" is the following: the UI client receives keystrokesand interprets the commands they correspond to. As soon as one of the commandsis not just local UI manipulation, but a request to change the game state,such a request is packaged and sent to the server (e.g., a requestto move a hero to the north). The server responds "not possible,there is a wall" or reacts by sending to clients (to all UI and AI clientsthat can see the event) a series of game state changing responses.AI clients, likewise, send to the server requests, generated basedon the changing game state and the AI goals of each AI faction.
Further information
For more information, visit the wiki4and see PLAYING.md,CREDITSand COPYLEFT.
Have fun!