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JamJar uses an Entity Component System (ECS) design at its core, this pattern drives much of the architecture of the engine.


ECS design is splitting up the engine and any games that use it into Entities, Components, and Systems. These three components should be able to cover any functionality that a game needs.

An entity is a single thing in the game, for example a player, a bullet, or a camera.

A component is a piece of data that is attached to an entity, for example position (Transform), an image (Sprite), or the player's number of lives.

A system is some logic that can operate on entities and components to interpret them and modify them, for example the SpriteSystem which takes Sprite descriptions and converts them into a format that the render pipeline can use to draw shapes.


  • Decoupling of game logic, helps keeps direct dependencies to a minimum.
  • Consistent method of structuring the game and engine.
  • Things in the game are grouped together using composition rather than inheritance, meaning traits can be easily added and removed from things, and shared between things.


  • Can be difficult to understand when coming from an Object Oriented Programming approach.
  • Sometimes can result in a lot of 'boilerplate' type code for some simple functionality.
  • Concurrency is hard.