Thank you so much to everyone for your compliments!

How did you generate the spiral guidelines?

Blotbot, I used a compass and drew half-circles, alternating between two centers. It works like this:

1. Draw half a circle with a compass.

2. Move the compass center over by the distance you want between your spirals (i.e., your desired interlinear distance.). The adjusted position should be on the line created by joining the two points of your semi-circle.

3. Put the pencil end of the compass on the end of the outer semi-circle. This will require compressing the compass a little bit, because the new center point is closer to the semi-circle. Draw a new semi-circle. This will be slightly smaller, and by the time it lines up with where you started, it will be farther inside.

4. Move your compass center back to the original center, and put the pencil on the end of this new semi-circle. Again, you will have to shorten the compass a bit. Draw a new semi circle, which will end up inside the second semi circle.

5. Repeat until you're out of room, always alternating between the two centers.

I should mention that this is known as the "Archimedean spiral." If you search for "how to draw an Archimedian spiral" you'll find tutorials with pictures.

Cecilia, I've never heard of three and four center spirals! What do they look like? Google doesn't seem to know the term, and I can't quite figure out how to draw them according to my algorithm above.