 ly = -height / 5;

    ctx.save();
    ctx.translate(lx, ly);

    ctx.fillStyle = colors.arrow;
    ctx.strokeStyle = colors.arrow;
    var numArrows = 5;
    for (var ii = 0; ii <= numArrows; ++ii) {
      var u = ii / numArrows;
      var x = (u * 2 - 1) * 70;
      ctx.save();
      ctx.translate(x, 0);
      ctx.rotate(direction);
      diagram.arrow(ctx, 0, -20, 0, 20, false, true, 0.5);
      ctx.restore();
    }
    ctx.fillText(lang.lightDir, 0, -30);

    ctx.restore();

    var sx = 0;
    var s