An asterism is a pattern people can see in stars, and while there is a fixed set of true constellations we can come up with as many asterisms as we like.

Asterism is a project in operationalizing operational logics to the extent that they can be composed to form game engines.

Current authors: Cynthia Li, Joseph C. Osborn
Previous authors (2019–2022): Katiana Wieser, Carl Bell, Julie Ye, Jayce Garner

The prototypes directory contains games and game engines implemented on top of asterism.

This means that instead of a monolithic update() function which combines different logics and extremely concrete instantiations of abstract processes, the game loop arbitrates its rules by configuring and calling out to a variety of logics. For example, the game code might project the game state out to a set of colliders for a specific type of collision logic, allow the collision logic to update itself (detecting contacts and halting motion of blocked colliders), then unproject the collision-specific state out to the full game state. (For efficiency this projection/unprojection step could even be a no-op depending on how the game state is represented.) Afterwards, the game could process the contacts to perform game specific actions like destroying blocks or winning points.

For rendering, the collision logic can be configured to map its provided communication channel (the positions and extents of objects, the locations of contacts) onto an output device (a framebuffer, 3D renderer, or terminal). The game can then make use of this mapping to position and draw game content.

As another example, consider the control logic which is initialized with appropriate input devices and configured to map these onto the specific game’s abstract inputs (“move the player character in the X direction”, “confirm a menu option”, etc). Later the values to which the user has controlled these abstract inputs can be queried to e.g. effect changes in the velocities of bodies in the physics logic.

Ceptre is a programming language by Chris Martens that allows a user to model a game through predicates and rewrite rules. We’re looking to be able to convert Ceptre games to Asterism ones because both seek to target game genres beyond 2D platformers and top-down dungeon crawlers. We’re interested in the potential for formal overlap between the two systems.

boxsy-ceptre is a case study for converting a dungeon crawler written in Ceptre to Asterism games through the boxsy engine.