Images via: (clockwise from top left) 
“Layered, mixed shadows” by Peggy Reimchen, “44:365 Paper shadow” by Jin Choi, “Shadows, Bran Castle, Romania” by Dimitry B. (cropped from original), “office chair shadow” by Dean Hochman (cropped from original), “chess shadows” by Cyndy Sims Parr (cropped from original), “Dune Shadows #1” by Shawn Allen, “Shadows” by Kevin Dooley
