g-raj-k/arduino-smoke-detector-monitor ? reverse-engineered prompt

Build me a local web app for monitoring an Arduino Nano smoke detector setup.

It should connect over USB serial in the browser, read two MQ 2 sensors on A0 and A1 at about 10 updates per second, and show the readings in a clean dark dashboard. I want a simple status view for current smoke level, peak level, and how fast smoke is rising, plus an alert when the buzzer pin should turn on. Include a quick way to calibrate both sensors to clean air, and a way to adjust the warning thresholds from the UI.

If possible, make it feel like an incident monitor with a 3D building view, sensor locations I can move around, and a smooth color change from safe to danger as smoke increases. It should also handle a demo mode when no hardware is plugged in, and show a clear no signal state instead of fake alarms. If you need to look up current browser serial docs or Three.js details, feel free to do that.