In music, going from B to C is a half step because there is no sharp or flat (from black notes on a piano) in between the two notes. Whenever two notes are strictly consecutive (nothing in between), they are considered half steps from each other. Meanwhile, whole steps are where there is something (only one, though) in between the two notes.
refer to these websites for more info on both illusions 1- thevirtualinstructor.com/hatchingcrosshatching.html 2- www.udel.edu/artfoundations/beg_paintingtechniques.html
