The table on which my computer rests is lined with a grey laminated sheet. Quite perfect for me to doodle when i've something that writes well in my hand. As i type, i see something drawn in red. We used a red glass marking pencil during my undergraduate days which apparently never wrote on glass. We struggled initially until we switched to OHP markers.
The figure in red appears to have faded a little. I can't decipher it out, maybe a few flames of fire bunched together. When rubbed with a finger, the colour sticks to the skin as the figure is blurred.