float x=0;
 float y=0;

 float color1=0;
 float color2=0;
 float color3=0;

float velocity_x=7;
float velocity_y=3;

float x_length = 800;
float y_length = 800;

float diameterc = 150;

float x_left_bound;
float x_right_bound;

float y_upper_bound;
float y_lower_bound; 

float diameter_increase;

void setup() { 

 size(800,800);

}

void draw() {

  background(125,125,125);

 fill(color1,color2,color3);

x_left_bound = diameterc/2;
x_right_bound = x_length-(diameterc/2);

y_upper_bound = diameterc/2;
y_lower_bound = y_length-(diameterc/2);

  if ((x &rt; (x_right_bound-(velocity_x/2))) && (x < (x_right_bound+(velocity_x/2)))) {

    velocity_x=velocity_x*-1;
    color1 = random(255);
    color2 = random(255);
    color3 = random(255);

    if ( diameterc <= 750) {
    diameterc=diameterc+10;

    }
  }

  else if ((velocity_x < 0) && (x < (x_left_bound-(velocity_x/2))) && (x &rt; (x_left_bound+(velocity_x/2)))) 

  {

    velocity_x=velocity_x*-1;
    color1 = random(255);
    color2 = random(255);
    color3 = random(255);
     if ( diameterc < 750) {
    diameterc=diameterc+10;

    }

  }

 if ((y &rt; (y_lower_bound-(velocity_y/2))) && (y < (y_lower_bound+(velocity_y/2)))) {

    velocity_y=velocity_y*-1;
    color1 = random(255);
    color2 = random(255);
    color3 = random(255);
     if ( diameterc < 750) {
    diameterc=diameterc+10;

    }
  }

  else if ((velocity_y < 0) && (y < (y_upper_bound-(velocity_y/2))) && (y &rt; (y_upper_bound+(velocity_y/2))))  {

    velocity_y=velocity_y*-1;
    color1 = random(255);
    color2 = random(255);
    color3 = random(255);
     if (diameterc < 750) {
    diameterc=diameterc+10;

    }

  }

  x=velocity_x+x;
  y=velocity_y+y;

  ellipse(x,y,diameterc, diameterc);

}