Introduction

You are going to create a 2-player game to see who has the fastest reactions. The game will work by showing an image after a random amount of time - whoever presses their button first is the winner.

Instructions: If you’re reading this online, wait for an image to display on the micro:bit below and then press A or B first to see who is the fastest.

Step 1: Wait for it!

Let’s start by displaying an image after a random amount of time.

Activity Checklist

Go to jumpto.cc/pxt-new to start a new project in the MakeCode (PXT) editor. Call your new project ‘Reaction’.
Before displaying an image, the game should wait for a random amount of time.

Drag a pause block into the forever block and change the pause time to 1000 ms:

Add another pause block and then drag a pick random block to pause block and set its value to 4000:

Remember that 1000ms is 1 second, so there will be a pause of at least 1 second up to a maximum of 5 seconds (1000 + 4000 ms).

You can change the ‘1000’ and ‘4000’ numbers to change the minimum and maximum pause if you like.

After waiting, your game should show an image so that players know when to press their button.

Click ‘run’ to test your project. You should see your image appear after a random delay.
Add code at the end of the forever loop to display your image for 1 second and then clear the display.

Test your project. You should see your image appear randomly and then disappear.

Challenge: Choose your own image

Can you change the image that’s displayed?

Challenge: Choose your own delay

Change the numbers in your random block. You can speed up your game to make it harder, or slow it down to add suspense!

Step 2: Waiting for a winner

Let’s add code to wait until a button is pressed.

Activity Checklist

After displaying an image, you’ll need to wait until someone presses their button.

Another way of saying this is that you’ll need to wait as long as button A and button B have not been pressed.

To do this, add a while loop from the ‘Control’ section. The while loop should be added in just after the draw block.

Drag an and block from ‘Logic’ to your while block:

Drag a not from ‘Logic’ into the left hand side of the and:

Drag an button A is pressed block from ‘Input’ to after the not:

Repeat the 2 steps above to add not button B is pressed into the right side of your while loop.

You can then add a very short (20ms) delay, so that your while loop waits as long as a button hasn’t been pressed.

Test your project. Your game should now display an image and then wait as long as buttons A and B have not been pressed.

Step 3: Who is the fastest?

Let’s find out who pressed their button first.

Activity Checklist

If button A was pressed, we want to point to player A. To do this, add an if block after your while loop, and replace test with button A is pressed.