This article describes my modifications to the Entity Component System (ECS) architecture pattern to better support a turn-based game loop. This involves implementing game logic in actions which describe changes to the game’s state, and rules which prevent certain actions, and trigger additional reactions. The combination of actions and rules replace the traditional idea of systems.

This is the first of a series of posts I’m writing to explain the inner workings of the game engine I used for my 7DRL: Apocalypse Post. It motivates one of the problems I set out to solve with the engine - how to represent the types of game entities.

Apocalypse Post is a procedurally-generated, turn-based tactical shooter set in a post-apocalyptic future, where you carry mail between survivor camps in your trusty delivery van, all the while fending off attacks from bandits and zombies. Between each delivery run, buy weapons and armour to upgrade your van to cope with ever-increasing numbers of enemies.

I spent the night polishing, play-testing, balancing and fixing some minor bugs. I consider the week to have been largely successful. The game turned out roughly like what I imagined at the start of the week.