Small Untitled RPG Devlog 2

UI, Interaction, Event System, First NPC

Since the last devlog there were 10 commits between 2019/01/27 and 2019/02/15, totaling 21 commits. I have worked 28 hours during this period, bringing the total to 48 hours.

I started out by adding new type of objects to my Tiled map.


A bit more messing around and I can now have basic message interaction in the game.

That included adding overlay UI system, some refactoring, support for nineslice scaled ui elements. Handling events between various ECS systems without tight coupling (Keyboard Input System sends an Interaction event that Interaction System then handles).

I also refactored how I change what animation to play on a character. Before it was explicit from keyboard input, but planning forward I changed it to be implicit from actor’s velocity. This will work with different input systems (point and click) and also for characters controlled via AI.

Then I added our first NPC. Meet Rufus.


Since I wanted to play with our new friend, it was time to add some AI.

I decided to implement Behavior Trees. In the ECS spirit, they are completely stateless (the tree/logic itself doesn’t store any data, everything is kept on entities). I define them in XML (which will be improved later), and they compile down to basically an array of functions. Since they are stateless, the same tree can be used to run any number of entities.


That’s it for this dev log. As for ECS changes, I’ve renamed Movement system into InputMovement, added AISystem, ActorAnimation, InteractionSystem systems. Also added AIState and Interaction components. For other parts, added UI and Overlay Phaser scenes, and MessageBoard UI element.

In the next dev log I will talk more about Behavior Tree AI and my approach to it.