b = 0;

c = 0;

d = 0;

function setup() {

  createCanvas(400, 400);

  frameRate(243676034296920376);

}

​

function draw() {

  background(0);

  stroke(255);

  line(200,200,mouseX,mouseY);

  var x = ave(200,mouseX);

  var y = ave(200,mouseY);

  fill(a,b,c);

  ellipse(x,y,d+30,d+30);

  //challenge: use the ave function again to make

  //a green dot half way between the center and the

  //red dot

  var x2 = ave(x,200);

  var y2 = ave(y,200);

  fill(b,c,a);

  ellipse(x2,y2,d+30,d+30);

  var x3 = ave(x,mouseX);

  var y3 = ave(y,mouseY);

  fill(c,a,b);

  ellipse(x3,y3,d+30,d+30);

  a = random (0,255);

  b = random (0,255);

  c = random(0,255);

  if(keyIsDown(UP_ARROW)){

  d = d + 1;

}

  if(keyIsDown(DOWN_ARROW)){

  d = d - 1;

}

  if (d < -30){

  d = -30;

}

}

function ave(num1, num2){

  return (num1 + num2)/2

  // replace with code to return average of the two arguments

}

​

​