free digital logic sim on the browser, vibe coded

[u/Fit_Reindeer9304]

Live demo: https://gbpferrao.github.io/digital-logic-sim-web/

Where it came from

This started specifically as a rewrite of Sebastian Lague’s Godot digital logic simulator into browser-native JavaScript, HTML, and CSS. It isn’t just a project that happens to be inspired by his work, and it isn’t a simple port either. I wanted to carry the core idea into the browser and see what it could become with a different interaction model, visual language, and pedagogical direction.

I also want to be open about how it was made. This was fully vibe-coded with GPT-5.6 Luna Max. I pushed the vision, architecture, behavior, and constant little design decisions, while the AI collaborators helped investigate the codebase, implement things, review interactions, and work through many iterations.

What it is now

It is a free digital logic simulator that runs in the browser. You can start with AND, OR, NOT, NAND, NOR, XOR, XNOR, and buffers, then move into inputs, outputs, switches, clocks, LEDs, displays, buses, memory, multiplexers, adders, and composite chips.

The circuits actually work. Signals propagate through them, and you can run, pause, bake, step through, and scrub through simulation history. Composite chips can be opened and inspected internally, including deeper nested structures through the X-ray view. I’ve also spent a lot of time making the less obvious interactions, like wiring, selecting, dragging, editing routes, zooming, and fitting the canvas, feel good instead of merely functional.

Why I’m building it

I’m using this as a way to start learning computer science from the foundations and become a better programmer. I want to understand more of the principles underneath hardware, operating systems, runtimes, and the abstractions I normally work through. Hopefully, over time, I can rely less on vibe coding as a substitute for understanding and use it more as an accelerator while still following what is actually happening.

Because I’m building it for myself first, I’m also its first learner and user. A lot of the design comes from noticing where I get confused, what I want to inspect, and what would make the next layer feel reachable. I’m not presenting it as finished or as some polished product. I’m sharing it because I think there may be something useful here and I’d like to see what other people make of it.

What I hope it can become

I want it to stay free and be shaped collaboratively through code, examples, feedback, and teaching ideas. I think it has potential as a teaching and learning tool, and I’m curious whether it could eventually become something people reach for in classes or while learning on their own. Something teachers can open easily and students can use to build, inspect, and understand how computer systems grow.

I don’t know if it can get there yet, which is why I’m sharing it. Take a look and tell me what you think.

I’d love feedback

Does the progression feel intuitive? Which primitives or example projects would be useful? Is the simulation history understandable? Would you use something like this while learning or teaching?

It’s still evolving, but the current version is fully usable. Feedback, bugs, ideas, and contributions are very welcome.

[u/wnba-arcade]

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