I built a 3D circuit simulator with a real SPICE-style solve

## Why I built this

I wanted a circuit simulator I could open in a browser tab and start building immediately — no install, no account wall, no desktop software from 2009. Most free options are either flat 2D schematic tools (great for accuracy, rough on beginners) or heavily gated freemium products.

So I built CircuitForge: a 3D breadboard-style workspace where you place real components, wire them up visually, and simulate DC circuit behavior in real time.

## What it does

- Full 3D workspace — orbit, zoom, and place components like you're looking at a real breadboard

- Wire components together and run live simulation

- A real Modified Nodal Analysis (MNA) solver computes exact node voltages and branch currents — the same underlying technique professional SPICE tools use, not an animation or approximation

- Components include resistors, LEDs, batteries, switches, capacitors, inductors, diodes, and transistors

- An AI assistant (powered by Gemini 3.6 Flash) that looks at your circuit state and helps explain why something isn't working

- Save and share circuits with Google sign-in

## How it's built

**Frontend:** React 19, TypeScript, and Vite. Three.js handles the 3D canvas, camera controls, and raycasting for placing and selecting components. State is managed with Zustand — Redux felt like overkill for this scale of app.

**Backend:** Express hosted on Render, proxying Gemini 3.6 Flash so the API key never touches the client. Firebase handles Google auth and Firestore stores saved circuit designs.

**SEO/Crawling:** I wrote a build-time pre-renderer (`scripts/prerender.tsx`) so tutorial pages generate real static HTML instead of shipping a blank SPA shell to search crawlers.

## What it can't do (yet)

To be upfront: this is not a SPICE-level simulator. It handles DC steady-state analysis well, but it doesn't do full transient or AC frequency-domain analysis the way LTspice or ngspice do. The component library is still growing — every new part needs a custom 3D model and wired-up connection points, which takes time solo. Touch controls for wiring on mobile are also still rough.

## Try it

It's live and free at luvaai.in — no signup needed to start building. If you're into 3D web rendering, circuit simulation, or just want to poke holes in the wire-routing UX, I'd genuinely like the feedback.