Impossible pushing

The rules of the minigame are simple : You play the game, and then you try to describe a level that would be impossible to beat. I then make a level with one extra rule to make that level possible. Basically a reverse UNIQUENESS.

Some clarifications :

• You can't edit previous levels.
  
• You need to make sure that the new level's rules won't make the previous levels impossible.
• I can add new objects, but you can't directly tell me to do it.