pxt-calliope/olddocs/js/lessons/while-counting/challenges.md
2016-04-15 14:37:25 -07:00

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# digi yoyo challenges
These challenges will teach you how to create a counter 10 to 1. #docs
**Challenge 0**
### @video vimeo/134459911
[This guided tutorial](/lessons/digi-yoyo/tutorial) will teach you how to make a counter from 0-9 using a while loop.
```
count = 1
while (count < 10) {
basic.pause(1000)
basic.showNumber(count, 150)
count = count + 1
}
```
**Challenge 1**
How about we create a counter that counts backwards from 10 to 1? Let's add a while loop that executes only when `count` is greater than 0.
```
count = 1
while (count < 10) {
basic.pause(1000)
basic.showNumber(count, 150)
count = count + 1
}
while (count > 0) {
}
```
**Challenge 2**
Inside of the while loop, let's add `pause->(1000)` so that we have a pause between each number as it's counting down. Also, let's show `count`!
```
count = 1
while (count < 10) {
basic.pause(1000)
basic.showNumber(count, 150)
count = count + 1
}
while (count > 0) {
basic.pause(1000) // ***
basic.showNumber(count, 150) // ***
}
```
* Run the code to see if it works as expected.
**Challenge 3**
### @video vimeo/134449661
Now, we need `count` to decrease by one after the micro:bit has displayed the value of `count`.
We can do this by adding this line:
```
count = count - 1
```