pxt-calliope/docs/reference/js/lessons/counter/challenges.md
2016-03-29 21:17:57 -07:00

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# counter challenges
Coding challenges for the counter tutorial.
## Before we get started
Complete the following [guided tutorial](/microbit/lessons/counter/activity) At the end of the tutorial, your code should look like this:
```
let count = 0
input.onButtonPressed(Button.A, () => {
count = count + 1
basic.showNumber(count, 150)
})
```
### Challenge 1
### @video td/videos/counter-1-2
Let's add the code to `count` when `B` is pressed. Add an event handler with `input->on button pressed(B)` then add the code to `count`.
```
let count1 = 0
input.onButtonPressed(Button.A, () => {
count1 = count1 + 1
basic.showNumber(count1, 150)
})
input.onButtonPressed(Button.B, () => {
count1 = count1 - 1 // ***
basic.showNumber(count1, 150) // ***
}) // ***
```
### Challenge 3
Now let's try to reset the counter when the BBC micro:bit is shaken. You will need to register an event handler with `input->on shake`.