pxt-calliope/docs/lessons/night-light/offset-image/activity.md

offset image challenges

Coding challenges for the offset image tutorial. #docs

Before we get started

Complete the following exercise. Your code should look like this:

offset = 0
basic.forever(() => {
    if (offset == -4) {
        basic.showString("Push button A", 150)
    }
    images.createImage(`
. . # . .
. . # . .
. . # . .
. # # # .
. . # . .
`).showImage(offset)
})
input.onButtonPressed(Button.A, () => {
    offset = offset + 1
})

Challenge 1

Create a condition for if button B is pressed. We want the image to move to the left when button B is pressed.

offset = 0
basic.forever(() => {
    if (offset == -4) {
        basic.showString("Push button A", 150)
    }
    images.createImage(`
. . # . .
. . # . .
. . # . .
. # # # .
. . # . .
`).showImage(offset)
})
input.onButtonPressed(Button.A, () => {
    offset = offset + 1
})
input.onButtonPressed(Button.B, () => {
    offset = offset - 1 // ***
}) // ***

• Run the code to see if it works as expected.

Challenge 2

@video td/videos/offset-image-2

Now we want to make sure that the button does not go off the screen to the right. Add a new line that checks to see if offset = 5 after button A is pressed.

If offset = 5 then prompt the user to move the image to the left by displaying the text: "Push button B".

offset = 0
basic.forever(() => {
    if (offset == -4) {
        basic.showString("Push button A", 150)
    }
    if (offset == 5) {
        basic.showString("Press Button B", 150) // ***
    }
    images.createImage(`
. . # . .
. . # . .
. . # . .
. # # # .
. . # . .
`).showImage(offset)
})
input.onButtonPressed(Button.A, () => {
    offset = offset + 1
})
input.onButtonPressed(Button.B, () => {
    offset = offset - 1
})

• Run the code to see if it works as expected.

Challenge 3

Now make sure the image does not go off the left side and if it does, prompt the user to push button A.