When I was at Michael’s getting a mirror, some slate, and a few other things, I also got a really nice birch round. It had me thinking that I wanted to play with a mix of trace and something I’ve seen online elsewhere. Hello to my sense of humor.
Yes, sharpie. Any marker should work, though, so long as you have high contrast to the white tile. Dry or Wet erase would also do well, though maybe less likely to smudge the sharpie.