This is my 2d game engine in C++ that I use to build games. It uses an ECS architecture (entity component system) and is very much a work in progress!
To ease with development, and since the classes are relatively compact, the source code is in header files only at this point. This makes it easier/more flexible to use in these early stages, as things are likely to change a lot. As the project grows, more platforms are supported, and when it is getting ready for an actual 1.0 release, this will probably change! The C++ Dos and Don'ts doc from Chromium, here, is a good resource to follow in the future (note to self!).
This engine is currently being used to develop a game based on a 2d (isometric!) grid, where objects act on a fixed time scale. Think of it like a music sequencer, where along fixed time intervals notes are fired, creating music.
The idea of this engine is that users can create a grid (defined in algorithms/graph.hpp) and create Behaviours for objects placed on that grid. A Behaviour is really just a vector of lambda functions and some other bits, which the NpcAiSystem (name will likely change) takes and sequences. The system will take all the behaviours, and fire the next behaviour for all registered entities at a user defined time interval. It can also, instead of the next behaviour, get the previous one, which is useful as a "go back in time" mechanic or an undo mechanic etc.
There's a small example program under example which shows how to set up an isometric grid with tiles from a spritesheet, animate it via the animation system, and add a timeline of behaviour ticks with the AI system.
At the moment, it probably does not make a ton of sense to use this early-stage game engine, unless you really are intrigued by the graph + time sequencing features and don't mind breaking changes, or if you want to help develop this!
Thanks for checking this out!