keep pupils inside the whites

The whites are drawn as circles on the yellow face.
Ideally they would show through clear circular holes in the face.

A similar effect can be achieved by drawing a yellow ring around the white.
The ring is drawn after the pupil is drawn.

That is, a circular outline using a thick line (40 pixels).
The original eye white has diameter 100 pixels.
ring diameter = white diameter + line thickness

  // Rings
  noFill();
  stroke(255, 225, 0);
  strokeWeight(40);
  var diam = 100 + 40;
  ellipse(width/2 - 80, height/2 - 60, diam, diam);
  ellipse(width/2 + 80, height/2 - 60, diam, diam);