//Dennis Malcolm

class Ball
{
    float d;    // diameter
    float x;    // x position
    float y;    // y position
    float sx;    // speed in x direction
    float sy;    // speed in y direction
    float dx;    // x direction, must be 1 or -1
    float dy;    // y direction, must be 1 or -1
    
    Ball()
    {
        // populate the arrays with initial values
        d = 50;
        x = random(width);
        y = random(height);
        sx = random(20);
        sy = random(20);
        dx = (boolean(round(random(1)))) ? 1 : -1;
        dy = (boolean(round(random(1)))) ? 1 : -1;
    }
    
    void display()
    {
        // draw the ball
        smooth();
        fill(255);
        ellipse(x, y, d, d);
    }
    
    void move()
    {
        // increment x and y by speeds and apply direction
        x += sx * dx;
        y += sy * dy;
        
        // test for x values less than zero and greater than width
        // if true, then reverse direction of x
        if (x <= 0)
        {
            dx = 1;
        }
        else if (x >= width)
        {
            dx = -1;
        }
        
        // test for y values less than zero and greater than height
        // if true, then reverse direction of y
        if (y <= 0)
        {
            dy = 1;
        }
        else if (y >= height)
        {
            dy = -1;
        }
    }
    
}