float x, y, xspeed, yspeed, radius;

int maxSpeed = 10;

void setup() {

size(640, 360);

pixelDensity(2);

xspeed = 5;

yspeed = 5;

radius = 25;

//Start at a random location!

x = random(radius, width-radius);

y = random(radius, height-radius);

}

void draw() {

background(0);

noStroke();

if (x < radius || x > width - radius) {

xspeed = constrain(random(xspeed, xspeed*2), -maxSpeed, maxSpeed) * -1;

//abs() returns the absolute value

if (abs(xspeed) == maxSpeed) {

xspeed = xspeed/5; //reset

}

}

if (y < radius || y > height - radius) {

yspeed = constrain(random(yspeed, yspeed*2), -maxSpeed, maxSpeed) * -1;

//abs() returns the absolute value

if (abs(yspeed) == maxSpeed) {

yspeed = yspeed/5; //reset

}

}

circle(x, y, radius*2);

x = x + xspeed;

y = y + yspeed;

}