pxt-calliope/docs/lessons/screen-wipe/activity.md
Sam El-Husseini e3975e65e5 pxt-microbit Accessibility PR ()
* Accessibility changes
2017-09-07 13:42:08 -07:00

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Markdown

# screen wipe blocks activity
Clear the screen by pressing buttons on the @boardname@
## ~avatar avatar
This activity will teach how to clear the screen by pressing button A on the @boardname@.
## ~
You can use the clear screen` function to turn off all the LED on the screen. Let's illustrate this concept with a small script where the user has to press the button A to turn off the screen. Let's start by adding the code to show an animation.
```blocks
basic.showLeds(`
# # # # #
# # # # #
. . . . .
. . . . .
. . . . .
`)
basic.showLeds(`
# # # # #
# # # # #
# # # # #
# # # # #
. . . . .
`)
basic.showLeds(`
. . . . .
. . . . .
# # # # #
# # # # #
. . . . .
`)
basic.showLeds(`
. . . . .
. . . . .
. . . . .
# # # # #
# # # # #
`)
```
We add another line of code that registers an *event handler* `on button pressed` *A* and calls `clear screen`.
```blocks
basic.showLeds(`
# # # # #
# # # # #
. . . . .
. . . . .
. . . . .
`)
basic.showLeds(`
# # # # #
# # # # #
# # # # #
# # # # #
. . . . .
`)
basic.showLeds(`
. . . . .
. . . . .
# # # # #
# # # # #
. . . . .
`)
basic.showLeds(`
. . . . .
. . . . .
. . . . .
# # # # #
# # # # #
`)
input.onButtonPressed(Button.A, () => {
basic.clearScreen()
})
```
*Run* the script in the simulator or on the @boardname@ to see how this works!
## ~avatar boothing
Excellent, you're ready to continue with the [challenges](/lessons/screen-wipe/challenges)!
## ~