pxt-calliope/olddocs/lessons/strobe-light/challenges.md

strobe light challenges

Coding challenges for strobe light.

Before we get started

Complete the following guided tutorial, your code should look like this:

for (let i = 0; i < 5; i++) {
    for (let j = 0; j < 5; j++) {
        led.plot(i, j)
        basic.pause(200)
    }
}

Challenge 1

Make the LEDs light up faster by changing the pause from 200 to 100 milliseconds:

for (let i = 0; i < 5; i++) {
    for (let j = 0; j < 5; j++) {
        led.plot(i, j)
        basic.pause(100)
    }
}

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

Challenge 2

Make the board light up by rows instead of by columns by swapping the i and j variables in plot(i, j).

for (let i = 0; i < 5; i++) {
    for (let j = 0; j < 5; j++) {
        led.plot(j, i)
        basic.pause(100)
    }
}

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

Challenge 3

Now that all the LEDs are lit up, let's make them turn off by reversing the strobe light pattern! You can use unplot to turn off a single LED.

for (let i = 0; i < 5; i++) {
    for (let j = 0; j < 5; j++) {
        led.plot(j, i)
        basic.pause(100)
    }
}
for (let k = 0; k < 5; k++) {
    for (let l = 0; l < 5; l++) {
        led.unplot(4 - l, 4 - k)
        basic.pause(100)
    }
}