Cow Room Escape is a significantly more difficult room escape game than its hard-shelled brother. For this game's ultimate combo-lock puzzle, you're looking for several different colored coins and you will really have to use your wits if you are to find them all.
Although it's a rather drab looking room, the puzzle contained within it is pretty sweet and it shouldn't take you more than 10 or 15 minutes. The room descriptions are all in Japanese, but thankfully you won't need them. Just be sure to click all sides of every object and you'll be out in no time.