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Put together a browser-based 3D circuit simulator over the last few weeks: https://luvaai.in The idea was to make something zero-install where you can just open a tab, drop components on a breadboard in 3D, wire them up, and run a quick simulation without signing up or dealing with desktop software like Multisim or LTspice.
How it's built
The frontend is React 19, TypeScript, and Vite, with Three.js handling the 3D canvas and raycasting for component placement. State is managed with Zustand (Redux was overkill for this).
On the backend, it's Express hosted on Render proxying Gemini 2.5 Pro for an AI helper panel that checks circuit state, plus Firebase for Google auth and saving designs to Firestore. I also wrote a build-time pre-renderer in scripts/prerender.tsx so the /learn tutorial pages generate static HTML for crawlers instead of rendering blank SPA shells.
What it can and can't do
It doesn't comes NEAR SPICE level simulation.
The simulation handles DC steady-state math — Ohm's law, series/parallel networks, Kirchhoff's voltage law, and basic component behavior including capacitors and inductors.
Where it falls short compared to something like LTspice or ngspice is full transient and AC frequency-domain analysis. The component library is also still growing since modeling and rigging custom 3D connection points in Three.js takes a while solo, and touch controls on mobile are rough for wiring.
Live at https://luvaai.in if anyone wants to check out the 3D interaction or run some circuits. Feedback on the Three.js performance or wire routing UX is welcome