To be honest, I found the game concept not expandable.
By the end of this short game, the player has already learned how to test the boxes one by one.
And that's a universal strategy against all puzzles of this type.
I know we can have some variants here, just put in every possible thing in a box pushing or grid movement game.
But the strategy would be all the same: Just check every box.
I guess a player will find the game boring once they notice the universal strategy. So I end up with only 10 levels.