I love this game!! On levels 41, 43, 45, 64, 74, 78 it's possible to end with more coins than the gold challenge! :D Those where all that I noticed, but there's probably others.
I think level 35 (Head Hurting) somehow broke? I've been doing the intended solution for awhile and nothing happens. Being vague so I don't spoil the solution for others.
 "Economical"){kind=icon}
 "Super Karoshi"){kind=icon}
 "Scalak"){kind=icon}
 "Pixel Zen"){kind=tracking}
 "Escape Game - Computer Office Escape"){kind=icon}