Edit in JSFiddle

var variable;
var r,g,b;
// declariation of a variable

function setup() {
  //createCanvas(windowWidth,windowHeight)
  createCanvas(480,360);
  // put setup code here
  variable= 255;
  r=0;
  g=0;
  b=0;
  // assigning a value

}

function draw() {
  // put drawing code here
  background(137);
  //b= b+1;
  //g= g+2;
  //robot body
  var size = 50;
  fill(255,255,0); //torso
  rect((width-size)/2,(height-size)/2,size,size*2);


//antennae
  line(width/2,(height-2*size)/2,width/2+size,(height-4*size)/2);
  line(width/2, //start x
    (height-2*size)/2, // start y
    width/2-size,//end x
    (height-4*size)/2);//end y

//head
    fill(255,0,0);
  ellipse( width/2,    (height-2*size)/2,         size);

fill(0,255,0); //legs
  rect(240,180+75,20,50);
  rect(240-20,180+75,20,50);

  //eye
  fill(255);
  ellipse( width/2,    (height-2*size)/2 -size/4,size/4);
  //eye
  fill(0);
  ellipse( width/2,    (height-2*size)/2 -size/5,size/6);
  //width/2,(height-2*size)/2

  //mouth
  line(width/2 -size/4,(height-2*size)/2+size/6,
  width/2+size/4,(height-2*size)/2+size/6);



}

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