import processing.core.*;

// Uses the Processing library to animate a simple drawing.
// The Processing library provides a framework for creating
// interactive drawings or animations.
public class ProcessingExample extends PApplet {

    // size of circle to draw
    private float size = 20.0f;

    // Called once for initial setup
    public void setup() {
        // window size
        size(500, 500); 
        // set framerate (in frames per second)
        frameRate(30);  
        // use smooth edges when drawing
        smooth();       
        // initial background color
        background(255);
    }

    // Called once per frame
    public void draw() {
        // new background to clear old frame
        fill(100, 100, 100, 20);
        rect(0, 0, width, height);
        // If mouse is down, draw a circle
        if (mousePressed) {
            fill(255);
            stroke(255);
            ellipse(mouseX, mouseY, size, size);
            // Pick new random by adding or subtracting a
            // random amount
            size = size + random(-5.0f, 5.0f);
            // constrain size to be with interval [5, 80]
            size = constrain(size, 5, 80);
        }
    }

    public static void main(String[] args) {
        PApplet.main(new String[] {"ProcessingExample"});
    }
}