Red Crossing, egg tempera on calfskin parchment, 9 1/2 x 7 7/8 in.
The image is basically very simple: a red rectangle and a long red stepped shape overlap a black rectangle. Some complexity is added with the shadows: angled bars at top, curves on the black. The large curved shadow reminds me of a proscenium arch, the red line below it becoming a presence on a stage. (Sometimes strange metaphors creep in to paintings.)
Red Crossing detail
This detail shows the translucency of the shadows. One thing I learned in art school, that has proved true in my years of painting from the motif, is that shadows are translucent, light is opaque. Translucency brings light into the darks.