pxt-calliope/docs/projects/rock-paper-scissors.md
2017-11-12 18:43:39 -08:00

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# Rock Paper Scissors
## Step 1
We want the @boardname@ to choose rock, paper, or scissors when you shake it.
Place a ``||input:on shake||`` block so when you shake the @boardname@, it will run part of a program.
```blocks
input.onGesture(Gesture.Shake, () => {
})
```
## Step 2
Add a ``weapon`` variable to store a random number computed with ``||math:pick random||``.
When you shake the @boardname@, it should pick a random number from `0` to `2`
and store it in the variable `weapon`. (This variable is named `weapon` because
rock, paper, and scissors are the weapons you use to battle your friends!)
```blocks
let weapon = 0;
input.onGesture(Gesture.Shake, () => {
weapon = Math.random(3)
})
```
In a later step, each of the possible numbers (`0`, `1`, or `2`) is matched to its own picture. The picture is shown on the LEDs when its number is picked.
## Step 3
Place an ``if`` block under the ``||math:pick random||`` and
check whether ``weapon`` is equal to ``0``.
```blocks
let weapon = 0;
input.onGesture(Gesture.Shake, () => {
let weapon = Math.random(3)
if (weapon == 0) {
}
})
```
## Step 4
In the ``if`` block, place a ``||basic:show leds||`` block that shows a
picture of a piece of paper.
```blocks
let weapon = 0;
input.onGesture(Gesture.Shake, () => {
let weapon = Math.random(3)
if (weapon == 0) {
basic.showLeds(`
# # # # #
# . . . #
# . . . #
# . . . #
# # # # #
`)
}
})
```
## Step 5
Add an ``else if`` block to the ``if`` block and check whether ``weapon``
is equal to ``1``.
Click on the gearwheel icon to open up the ``if`` editor; then drag and drop an ``else if`` block in the ``if`` editor.
```blocks
let weapon = 0;
input.onGesture(Gesture.Shake, () => {
let weapon = Math.random(3)
if (weapon == 0) {
basic.showLeds(`
# # # # #
# . . . #
# . . . #
# . . . #
# # # # #
`)
} else if (weapon == 1) {
}
})
```
## Step 6
Place a ``||basic:show leds||`` block under the else if and draw a **rock** image on the screen.
```blocks
let weapon = 0;
input.onGesture(Gesture.Shake, () => {
let weapon = Math.random(3)
if (weapon == 0) {
basic.showLeds(`
# # # # #
# . . . #
# . . . #
# . . . #
# # # # #
`)
} else if (weapon == 1) {
basic.showLeds(`
. . . . .
. # # # .
. # # # .
. # # # .
. . . . .
`)
}
})
```
## Step 7
Add a ``||basic:show leds||`` block with a picture of scissors to the ``else`` part.
You don't need to check if `weapon` 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``.
```blocks
let weapon = 0;
input.onGesture(Gesture.Shake, () => {
let weapon = Math.random(3)
if (weapon == 0) {
basic.showLeds(`
# # # # #
# . . . #
# . . . #
# . . . #
# # # # #
`)
} else if (weapon == 1) {
basic.showLeds(`
. . . . .
. # # # .
. # # # .
. # # # .
. . . . .
`)
} else {
basic.showLeds(`
# # . . #
# # . # .
. . # . .
# # . # .
# # . . #
`)
}
})
```
## Step 8
Your game is ready! Gather your friends and play Rock Paper Scissors!