var r;

var g;

var b;

​

function setup() { 

  createCanvas(600, 400);

  background(r,0,b);

} 

​

function draw() { 

  //col = (mouseX/600)*255

  //col = map(mouseX,0,600,0,255);

  //background(col);

  r = map(mouseX,0,600,0,255);

  g = map(mouseY,0,400,0,255);

  b = map(mouseX,0,600,255,0);

  background(r,g,b);

  noStroke();

  // fill(150,200,200);

  fill(0);

  ellipse(mouseX,200,40,40);

}