The code that controls the Arduino runs inside your browser (I haven’t explored the possibility of using node.js) which means that you can convert your Arduino (and inputs) into a remote control of sorts. Or do it the other way around and control the Arduino outputs from your browser. It’s really exciting when clicking a button in the browser causes a physical change in the real world (LED light turns on, a motor starts spinning, …), or when you wire a physical button to the Arduino and it causes your browser to do something. It really took me back to the beginning of my programming days, when everything was new and exciting and full of wonder.
Some of the things we built include: a blinking LED, an LED that changes colour randomly and a colour picker in the browser that sets the colour of the LED. As a final exercise we got to build either a “Simon says” game or a “Etch-a-Sketch”. I opted to build the “Etch-a-Sketch” and again it was really fun to see how rotating two potentiometers on the Arduino was causing lines to appear on the canvas in the browser.