some, errr, lines.

somelines.pde

size(400, 400);  // the default size is too small
smooth();        // i don't know why you wouldn't use this for images.
background(128); // 50% gray background

int lineCount = 20; // number of lines to be drawn
int circleDepth = 10; // how "deep" the circle is said to be.
int lineSpacing = height / lineCount; // how far apart the lines should be from one another

/* the lines should be half as wide as they are far apart, such that the positive
and negative space is equal. */
strokeWeight(lineSpacing / 2);

for(int i = 0; i < lineCount; i++) {

  /* draw lineCount number of equally-spaced horizontal lines. */
  int lineHeight = i * lineSpacing;
  noFill();
  stroke(0);
  line(0, lineHeight, width, lineHeight);
  
  /* if we're at the circle's "depth", draw the circle.  This will be drawn above the lines that
  were already drawn, but lines drawn in the future will be drawn in front of the circle. */
  if(i == circleDepth) {
    fill(255);
    noStroke();
    ellipse(width / 2, height / 2, width / 4, width / 4);
  }
}