Go to https://lines.chromeexperiments.com/drag/, start the experience and run this code in the console

gistfile1.txt

document.getElementById( 'loading' ).style.display = 'none';
var speed = .001; // changes the rate of rotation
var distance = 4; // changes the distance the point travels
function _update() {
	bAmDrawing = true;
	lastMouseX = 0; lastMouseY = 0;
	var a = speed * performance.now();
	var x = distance * Math.cos( a );
	var y = distance * Math.sin( a );
	stage.mousemove( { data: { global : { x: x, y: y } } }  )
}
function _animate() {
	_update();
	setTimeout( _animate, 1000 );
}
_animate();

But before executing, select the execution context to draw-container as the actual script needs to run inside the correct iframe

Right, when starting from the main page.
The instructions say "go to https://lines.chromeexperiments.com/drag/", to skip the embed altogether.

Oh, I had it open already and haven't noticed that the URL was different, my bad! Thanks :)