You can see level objectives in the pre-level pop up and at the top of a level. To clear a level you need to make sure you meet a level objective. Each level may have one or more of the following objectives.

Defeat the enemies

You can clear such a level by defeating all enemies. Some lizards can be stunned and removed by making fruit matches. Tougher enemies require you to hit them with Nibblers more than once! 

IMPORTANT: Beware of the Fishing Lizards, as they can catch and destroy your Nibblers!

Clear the mud

Match fruits or use Nibblers to clear all mud tiles on a level. Two-layer mud tiles need to be hit twice.

Collect fruit

Collect the required amount of fruit on a level by making matches and using Nibblers.

Rescue the fish

Free the helpless fish by leading them to water. If a fish is in the bucker, you need to break the bucket first by matching fruit next to it or hit it with a Nibbler before the fish is freed.