There are two different versions available: v1 and v3.764. Each version defines its own rules of engagement with every level it presents. It's your job to figure out exactly what is required to advance.
Use the mouse for interaction in these games: point, click, drag, whatever it takes.
I first came upon these bizarre little puzzle games about a year ago, but passed on them then because there are instances of profanity contained within: one as text on the screen, and the other in an audio clip. So, these games may not be suitable for a younger audience.
Mature content aside, <no>circles</no> is just the kind of Flash game I like to highlight here. The game illustrates creativity in interactive design principles and requires a think-outside-the-box approach to solving its many puzzles. It is the sort of thing that can spark inspiration, and I think you will agree that it is just right for a casual diversion. Click.