In case you're wondering, how in the heck to do that swirl in the middle of the Sunbeam sun . . . This is where to get the low-down.
These steps are not included in the pattern details.
To be clear, the circular space that represents the sun's center is your space to do whatever you want with embellishment (or not)! For me, some have had a simple ring of French knots around the outer edge of the circle, some with nothing but the blanket stitch to secure it, then I experimented with the swirl idea and it kinda stuck. Now it's my go-to Sunbeam center.
Be as creative with your stitches as you like!

CLICK HERE to Get a Sunbeam Kit
CLICK HERE to Get the Sunbeam PDF

To make the swirl center, I start my embroidery embellishments on my Sunbeam heart like I always do, with the felted wool shapes secured with fusible web to the cotton background fabric. Then I secure all the felted wool edges with a small blanket stitch (or your preferred stitch). My blanket stitch is made with size 12 perle cotton (in this case a bright yellow from ArtFabrik) and a size 5 embroidery needle.
For the swirl center. I use the disappearing ink marking pen from Quilters Select (ask for it at local quilt shops). There are a few disappearing ink pens out there, but I especially like this one for this task because it easily makes a bold line.
Plan ahead! If you want to mark now and sew later, you may find that your markings will have disappeared by the time you're ready to stitch. Mark and stitch all in one sitting, if you can.

,I am right handed, and I'm going to work a Portuguese Knotted Stem stitch for this swirl. If you're not familiar with this stitch, I created a video for your in the Stitch Library. As an alternative, a chain stitch is nice too.
I start marking along the outer edge of the circle, following the inner edge of the blanket stitches, working from left to right (because that's the direction I'm going to use for the stitching). When I am *almost* at the beginning of the circle, I continue drawing my line with a slight curve inward.
Instead of drawing a single-pass line like chalk on a chalkboard, I use small strokes, almost like paintbrush strokes, advancing deliberately a little at a time, and moving the fabric counterclockwise underneath my hand.

As I proceed around the circle with my short strokes, I stay about 1/4" away (or whatever distance you like) from the outer line that I'm echoing. I don't use a template, just a steady hand and those short, deliberate strokes.

There you have it.
It's not perfect, but it's a solid, visible line.
If necessary, I go over the line with those short paintbrush strokes to make sure the line is really bold.
If you find that some of the ink is setting on top of the wool, blot it carefully with a paper towel to absorb excess ink.
Now, you are ready to stitch!

As I mentioned earlier, I'm right handed, and I work the Portuguese Knotted Stem Stitch from left to right. This stitch has a little scallop or bump on one side of the stitch, and I want that bump to follow the outer edge of the swirl. To make that happen, as I stitch, I keep the outer edge of the circle (the part I'm stitching) away from me. What you see in the photo is what I'm seeing on my lap - I turn the fabric counterclockwise as I stitch so the outer edge is always farthest away from me.
For this stitch, I like to use a size 5 perle cotton and a size 3 milliner needle. Normally I am more inclined to use an embroidery needle for this stitch, because the looped part of the stitch is a little more comfortable with a shorter needle. However, I prefer the milliner needle here because it glides a bit better through the extra layer of fabric and wool.

I continue to work the swirl following the line.
When I get to the point where the lines nearly intersect, I am careful not to catch up the previous row with the looped part of the stem stitch.

As I approach the very center, my stitches get slightly closer together. To finish the last stitch, I sink the needle into the center and tie off with a double back stitch on the back.

That's it!
Any remaining visible drawn lines will likely disappear in a few hours.

In case you're interested, here's what the project looks like from the back.
I try to keep things neat, but I'm not meticulous.
This heart is already trimmed and ready for the final construction steps.