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# Karel the LED
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## ~avatar avatar
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Help Karel make LED art!
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## ~
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**Karel the LED** can't turn right, but he can make some great LED art!
The goal of this activity is to download the JavaScript code given below onto a board,
then USE the program to introduce new students to the @boardname @.
Students will not do the coding this time. They will be users to get familiar with the board.
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## How to play
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* ``A button`` **Turn Left**
Does not draw anything just changes the direction Karel (the flashing led) is facing
* ``B button`` **Move Forward**
Moves Karel forward one step and leaves the LED on behind him
* ``shake`` **Jump**
Moves Karel forward one step without leaving the LED on behind him
* ``A+B button`` **Hide Karel**
Shows or hides Karel (the flashing LED), to be used once your artwork is complete
* ``Reset button`` **Clear the board and restart**
Restart the program and clear the board
Note, that there is no way to erase, other than restarting.
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## ~
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See if you can make each pattern below using A, B, and shake. Once you have completed a challenge press A and B at the same time to hide Karel.
For patterns that you design decide which LEDs you want to turn on and then make that design with Karel.
## Spiral
## Right turn
## Eyes
## Smile
## Check
## First letter of your name
Figure out how to make the first letter of your name with the LEDs.
## Your design!
Make something fun!
Thanks for playing with Karel the LED!
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## ~
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```typescript
/**
* Karel the LED
*
* Copy this code into the JavaScript editor and program the board.
* Use the instructions above to complete the challenges.
*/
basic.forever(() => {
if (board.isKarelActive) {
led.toggle(board.karelX, board.karelY)
basic.pause(500)
}
})
input.onButtonPressed(Button.A, () => {
board.pressedA();
updateLeds();
})
input.onButtonPressed(Button.B, () => {
board.pressedB();
updateLeds();
})
input.onGesture(Gesture.Shake, () => {
board.shake();
updateLeds();
})
input.onButtonPressed(Button.AB, () => {
board.pressedAB();
updateLeds();
})
function updateLeds() {
for (let j = 0; j < 5 ; j + + ) {
for (let k = 0; k < 5 ; k + + ) {
if (board.ledState[j][k]) {
led.plot(k, j);
} else {
led.unplot(k, j);
}
}
}
}
const board = new Board();
enum Direction {
UP = 0,
LEFT,
DOWN,
RIGHT
}
class Board {
public isKarelActive: boolean;
public karelX: number;
public karelY: number;
public ledState: Array < Array < boolean > >;
private karelDirection: Direction;
constructor() {
this.isKarelActive = true;
this.karelX = 2;
this.karelY = 2;
this.karelDirection = Direction.UP;
this.ledState =[];
for (let i = 0; i < 5 ; i + + ) {
this.ledState.push([false, false, false, false, false]);
}
}
pressedA() {
if (!this.isKarelActive) {
return;
}
this.karelDirection = (this.karelDirection + 1) % 4;
}
pressedB() {
if (!this.isKarelActive) {
return;
}
this.ledState[this.karelY][this.karelX] = true;
this.moveKarel()
}
shake() {
if (!this.isKarelActive) {
return;
}
this.moveKarel()
}
private moveKarel() {
if (!this.isKarelActive) {
return;
}
switch (this.karelDirection) {
case Direction.UP:
if (this.karelY > 0) {
this.karelY -= 1;
}
break;
case Direction.LEFT:
if (this.karelX > 0) {
this.karelX -= 1;
}
break;
case Direction.DOWN:
if (this.karelY < 4 ) {
this.karelY += 1;
}
break;
case Direction.RIGHT:
if (this.karelX < 4 ) {
this.karelX += 1;
}
break;
}
}
pressedAB() {
this.isKarelActive = !this.isKarelActive;
}
}
```
## about the authors
This project was contributed by Dr. David Fisher a professor at [Rose-Hulman Institute of Technology ](http://www.rose-hulman.edu/ ). Dr. Fisher loves educational robotics and runs various outreach programming activities, including a summar camp, called [Connecting with Code ](https://connectingwithcode.org ), which gives a @boardname @ to each participant.
