Each level has a door, representing the objective of the level and the win condition. Each level is completed by touching the door with the character.
The door is a displayed as green block and is almost always visible at the start of a level. When the character touches it, the level is completed and a finishing page will be shown, displaying details about how the player completed the level.
Most levels only have one door, the only exception is the level 3 (Choice), which has two doors.