pxt-calliope/docs/getting-started/rock-paper-scissors.md

Rock Paper Scissors

~avatar avatar

Build a Rock Paper Scissors game with the @boardname@! You can play the game with a friend who has it on a @boardname@. You can also play it with friends who are just using their hands. (The game is built like a coin flipper, but with three choices instead of two.)

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Step 1: Getting started

We want the @boardname@ to choose rock, paper, or scissors when you shake it. Try creating an on shake block so when you shake the @boardname@, it will run part of a program.

Clear up the blocks and add the blocks below.

input.onGesture(Gesture.Shake, () => {
    
})

Next, when you shake the @boardname@, it should pick a random number from 0 to 2 and store it in the variable item.

Add a set block with a variable. Then add a pick random block, and store the random number in the variable, like this:

input.onGesture(Gesture.Shake, () => {
    let item = Math.random(3)
})

~hint

No one can predict random numbers. That's what makes them great for Rock Paper Scissors!

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Each possible number these blocks can make (0, 1, or 2) means a different picture. We will show the right picture for that number on the LED screen.

Step 2: Picking paper

Put an if block after the let block that checks whether item is 0. Make sure the if block has an else if part and an else part.

Next, add a show leds block that shows a picture of a piece of paper:

input.onGesture(Gesture.Shake, () => {
    let item = Math.random(3)
    if (item == 0) {
        basic.showLeds(`
            # # # # #
            # . . . #
            # . . . #
            # . . . #
            # # # # #
            `)
    } else if (false) {

    } else {

    }
})

Step 3: A random rock

Now we are going to add a new picture for the @boardname@ to show when another random number comes up.

Make the else if part check if the variable item is 1. Then add a show leds block with a picture of a rock.

input.onGesture(Gesture.Shake, () => {
    let item = Math.random(3)
    if (item == 0) {
        basic.showLeds(`
            # # # # #
            # . . . #
            # . . . #
            # . . . #
            # # # # #
            `)
    } else if (item == 1) {
        basic.showLeds(`
            . . . . .
            . # # # .
            . # # # .
            . # # # .
            . . . . .
            `)
    } else {

    }
})

Step 4: Suddenly scissors

Add a show leds block with a picture of scissors to the else part:

input.onGesture(Gesture.Shake, () => {
    let item = Math.random(3)
    if (item == 0) {
        basic.showLeds(`
            # # # # #
            # . . . #
            # . . . #
            # . . . #
            # # # # #
            `)

    } else if (item == 1) {
        basic.showLeds(`
            . . . . .
            . # # # .
            . # # # .
            . # # # .
            . . . . .
            `)
    } else {
        basic.showLeds(`
            # # . . #
            # # . # .
            . . # . .
            # # . # .
            # # . . #
            `)
    }
})

~hint

You don't need to check if item is 2 because 2 is the only number left out of 0, 1, and 2. That's why you can use an else instead of an else if.

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Your game is ready!

Click Download to move your program to the @boardname@!

Have fun!

Step 5: Are you the greatest?

Here is a way you can make your Rock Paper Scissors game better. When button A is pressed, the @boardname@ will add 1 to your score.

Open the Game drawer, and then add the block change score by 1 to your program, like this:

input.onButtonPressed(Button.A, () => {
    game.addScore(1)
})

Step 6: Prove you're the greatest!

After your @boardname@ can add 1 to the score, show how many wins you have.

input.onButtonPressed(Button.A, () => {
    game.addScore(1)
    basic.showString("WINS:")
    basic.showNumber(game.score())
})

Step 7: Staying honest

Success! Your @boardname@ can track wins! But what about losses? Use the Game drawer to subtract 1 from your score when you press button B.

Here are all the blocks you will need:

input.onButtonPressed(Button.B, () => {
    game.addScore(-1)
    basic.showString("LOSSES:")
    basic.showNumber(game.score())
})

Click Download to move your program to the @boardname@!

~button /projects

NEXT: PROJECTS!

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