This is an application that actually tries to do the Monty Hall problem. Two people play the role of a host and a challenger. There are two types.
Rotate to Use : Use a device alternately by two people.
Face to Face : Make a partition in the center of the screen with a piece of paper or something so that the challenger can't see the host's operation.

What is the Monty Hall Problem?
It is a problem for the challenger to consider what choice is best for the following game.
There are three closed doors in front of the challenger.
One door is a winning for a prize, and two doors are a miss.
First, the challenger chooses one door, then the host, Monty, opens one of the remaining doors that is missing.
The challenger now has to choose one of the following two options.
The first door selected is chosen as it is.
Re-select the remaining door that has not been opened.
Which door is most likely to win?

It is assumed that the host will open the wrong door after the challenger makes the first choice.