The circuit is just an image. The primitives are (i) connected wires which have undefined, 0 or 1 state during simulation (displayed brighter or darker in function of the state) and (ii) NANDs, which are little pixel triangles. During simulation the user can interact with any wire by clicking on it, toggling its state, which is cool for messing around when learning. The simulation uses a unit-delay event driven algorithm.
Then, on top of that there are little wire interfaces on the left side of the image that communicate with an external system. This external system is defined in lua and is simulated together with the main circuit (they alternate until convergence). By default there's a sandbox mode with a clock and a power-on-reset signal. The user can choose other "levels", where the API change and there are some problems to solve, from finding if a number is multiple of 3 to solving hanoi tower to finding if a number is prime. The idea is that if the user want to learn but not sure what to do they can try to solve these puzzles, or they can change the lua scripts to add their own stuff/interface for a custom project.
I've also included a small wiki (circuitopedia) with some basic digital concepts to guide those who are new or are a bit rusty. It's not super detailed but I guess it can at the very least present the concepts so the user can dig further on more serious material if they want to.
I developed the game in C with raylib, with scripting in lua/luajit. I've put the game on steam (for windows) and released the source code on github under GPLv3. There's also a web demo version on itch.io, even though it's a bit laggy: https://lets-all-be-stupid-foreva.itch.io/circuit-artist-dem... .
Feedback is appreciated!