OCD is "Obsessive Completion Distinction" and is an additional level of challenge while playing the game. To get OCD on a level, you need to complete additional requirements, which are either:

- Collecting additional balls, or
- Completing in fewer moves, or
- Completing in a certain amount of time.

You can view the OCD requirements for a level by pressing ESCAPE during level, and clicking OCD.

Once you have completed a level's OCD requirements, a white flag (or red flag in Chapter 4) will appear over that level in the chapter menu.