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Time bugs
If you get in trouble, just go back in time.

—Level description
[Impale Sticky]

Time bugs are small, fly-like insects found in World of Goo. When clicked by the player, they will take the player back one step in time, which reverses the last action of the cursor, such as adding a Goo Ball to a structure. This can be very useful for fixing mistakes, as time bugs can take you back before you made the mistake.

Time bugs first appear in the level Impale Sticky. While very useful for fixing mistakes, they can also cause them with their incessant flying around on-screen. When not paying attention, the player may sometimes accidentally click one and have to redo previous steps. Sometimes time bugs are numerous through a level and sometimes the player has to conserve them to fix mistakes that are made.

A single time bug