# nominetresearch/microbit-networking-book

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# Game 1: Shakey Donkey

## Introduction

Let’s put everything you have learnt so far into practice with a fun game. If you have not already seen it, Shakey Donkey is a micro:bit game that uses the radio [^1].

Shakey Donkey is played with two players, and it measures how fast you react to a Donkey appearing in your micro:bit. The game starts with shaking micro:bits. The moment your micro:bit displays a Donkey, you should shout “Donkey!” and shake your micro:bit to make it disappear. At the end, when you press the button A, if your micro:bit displays a happy face, you won!

In this chapter, you will practice:

1. the concept of group communication

2. using group or multicast address

3. sending and receiving messages

4. shake and button inputs

5. program variables and random numbers

### What you’ll need

``````2 micro:bits
1 whiteboard/board
boardmarkers/post-it notes
1 teammate
``````

## Programming: Playing Shakey Donkey

Description: To be able to play this game in groups of 2, you will set a unique group ID for your pair. Then you will program the Shakey Donkey game given to you in three parts in the the following figures.

Instruction: To set your groups, repeat the activity from Group communication: One to Many. Make sure your group IDs are unique!

The game is played by shaking your micro:bit each time the donkey appears on your display to get rid of it. So, first thing to do is to program what your micro:bit should do “On shake”. This is shown in the figure below.

``````let caught = 0
let me = 0
input.onGesture(Gesture.Shake, function () {
if (caught != 0) {
me += input.runningTime() - caught
basic.clearScreen()
basic.pause(Math.randomRange(0, 2000))
}
})
``````

!!! note "" Shakey Donkey program - Part 1: Shake your micro:bit to send your reaction time.

Notice that, in this first part, your program sends a number. So, you need a piece of code for handling a received number. This second part is shown in the next figure. Add it to your JavaScript Blocks editor program.

``````let you = 0
let caught = 0
caught = input.runningTime()
basic.showLeds(`
. . . . #
. # # # .
# # # # .
. # . # .
. # . # .
`)
})
``````

!!! note "" Shakey Donkey program - Part 2: Receive the other player’s reaction time, and display the donkey.

The third part, shown in the next figure, handles the case when the button A is pressed. This part of the program decides whether you won or not. Add this part into your program too.

``````let caught = 0
let you = 0
let me = 0
input.onButtonPressed(Button.A, function () {
if (me > you) {
} else {
basic.showIcon(IconNames.Happy)
}
me = 0
you = 0
caught = 0
})
``````

!!! note "" Shakey Donkey program - Part 3: Press button A to learn the result.

## Problems

Let’s first look at Part 1, in the first figure.

1. At the beginning, what is the value of the "caught" variable for both players? Does anybody need to change the "me" variable?

2. Who gets to send their "me" variable first?

Next, let’s look at Part 2, in the second figure.

1. When you receive a number, you set the "caught" variable. What does the "caught" variable mean?

2. You also change the "you" variable by the "receivedNumber". What does the "you" variable track?

Now, let’s look at both Parts 1 and 2.

1. Imagine you already started playing the program. You saw some donkeys appear on your display, and you shook them away. How did your "me" variable change? What is it equal to?

Finally, let’s look at Part 3, in the last figure.

1. How do you know you won? Does the other player know the result? How? Explain how the "me" and "you" variables are used to decide the winner.

2. How would you make sure you win this game?

[^1]: This game is by David Whale. We thank him for allowing us to use it in this book.