Using Circuit Playground with Arduino and Processing 3.

I’m trying to build a simple application for my school presentation.
I used Processing 3 to create an interactive animation, you can see it here:

I also want use Arduino Circuit Playground (right and left pushbuttons) to change the color or the background. I want ACP to send a signal every time I press a button, then Processing will catch it and transform into an action.

The problem is that I don’t know how program Arduino to send the signal every time the button is pressed. Can I get some help with my project?

The way to send a signal from Arduino tonProcessing is via a serial port. The serial library of Processing has examples that will help set up the serial port on the Processing side. This page will help for serial on the Arduino. Once you get the Arduino to talk to Processing you can send a signal when the button is pressed. Connect your switch (button) between ground and a digital input. Enable the internal pullup on the digital input with pinMode(pin, INPUT_PULLUP). Then if the state of the switch is LOW, it is pressed so Serial.print your message to Processing.