​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background("black");

​

  runningAverage = 0.97*runningAverage + 0.03*mouseX; 

  var col1 = color("Fuchsia"); 

  var col2 = color("Yellow"); 

  var myFillColor = lerpColor (col1, col2, runningAverage/width); 

​

  strokeWeight(5);

  stroke(myFillColor);

  line (runningAverage, 0, runningAverage, height); 

  noStroke(); 

  fill(myFillColor); 

  circle (200,200, runningAverage/width * 200); 

}

​

​