void setup()
{
  size(800, 300);
  background(255, 0, 0);
  x = 0;
}

float x; 
void draw()
{
  x = x+5;
  fill(0, 0, 255);
  stroke(255);
  strokeWeight(2);
  ellipseMode(CORNER);
  ellipse(0, 0, 100, 200);
  
  rectMode(CENTER);
  rect(width, height, 100, 200);
  
  fill(0, 255, 0);
  rect(width/2+x, height/2, 50, 50);
}