Serial.println() numbers — a single value like analogRead(A0), several space- or comma-separated values like x,y,z, or labelled pairs like temp:25.3,hum:60 — then open the Serial Monitor. They'll be drawn here as live, auto-scaling traces.serial.onValues(), send commands with serial.send(). Hook up web buttons & sliders, play sounds, draw on a canvas. Open the Serial Monitor to connect a board (the demos also work without one).English is a two-pane IDE. On the left you write what you want in plain English; on the right an LLM keeps a working translation in your chosen language — Arduino C++, Python, Ruby or JavaScript. Click any line on either side and the matching region on the other side lights up, with a ribbon linking them; click a line in the code pane to also drop a one-line gloss of what it does right below it, with an explain button for a fuller plain-English sentence. When the target is Arduino C++ you can Verify (compile in the cloud) and Upload the result to a connected board over Web Serial, then watch it with the Serial Monitor.
Buttons
Serial.print()s.Web Serial needs Chrome / Edge / Opera, served over http://localhost or https://. Flashing is wired for ATmega328P boards (Uno, Nano, Pro Mini); other boards still compile.
/openai/* on this page's server — i.e. the bundled serve.py, which forwards them to api.openai.com (the browser can't call it directly because of CORS). serve.py uses the $OPENAI_API_KEY from the shell you started it in; if you paste a key here it's sent through the proxy instead and stored only in this browser's localStorage.https://api.openai.com/v1 only if you're sure your environment allows browser CORS, or point it at your own proxy.serial object:
serial.onValues(fn) → fn({vals, order}) for each labelled/numeric line,
serial.onLine(fn) for the raw text, serial.send("…") to send a line to the board,
serial.connected / serial.onConnect(fn) / serial.onDisconnect(fn), and
serial.values (latest value per label). Open the Serial Monitor to connect a board. No board needed for the on-screen controls.