This is how the magic trick works.

The on start block sets the micro:bit's radio group.

A micro:bit can communicate with any other micro:bit with the same radio set group number.

In the example below it is set to 8.

The micro:bit sending out data is called the transmitter.

The micro:bit receiving the data is called the receiver.

Transmitter code Receiver code

Study the code above.

You will see that both micro:bits are set to radio group 8 so that they can communicate with each other.

Transmitter code

The transmitter's radio send number block transmits data to the receiver micro:bit when a button is pressed.

If button A is pressed it will send  1.

If button B is pressed it will send  0.

Receiver code

The receiver's on radio received block sets a variable called 'number' to the data received.

If 'number' = 1 the receiver micro:bit will display a happy face.

If 'number' = 0 the receiver micro:bit will display a sad face.

Its not magic, its rocket science!