// this is a comment. not code.

// here's how to move the turtle:
forward(50);
right(90);
left(90);

// reset the position and rotation
// of the turtle:
home();

// tell it when to draw and when not to draw:
penUp();
forward(50);
penDown();

// change the color of the line:
// (using a CSS3 color definition)
pushColor('red');
pushColor('rgba(255,0,0,0.5)');
pushColor('#BEEEEF');
pushColor('none');

// reset the color to what it was before:
popColor();

// change the fill color of the shape:
// (using a CSS3 color definition)
pushFillColor('gray');
...
popFillColor();

// change the width of the line:
// (in pixels)
pushWidth(2);
...
popWidth();

// change the opacity of the shape/line:
// (from zero to one)
pushOpacity(0.5);
...
popOpacity();

// position the shape/line over or under:
pushLayer(5);
...
popLayer();

// define a variable:
var distance = 50;

// use a variable:
forward(distance);

// define a function:
function moveForward50 () {
  forward(50);
}

// call a function:
moveForward50();

// display something for debugging:
console.log(distance);

// make a decision:
if(distance > 30) {
  console.log('distance is '
      + 'greater than 30');
} else {
  console.log('distance is '
      + 'less than or equal to 30');
}

// functions can have parameters:
function moveAndTurn (dist, rot) {
  forward(dist);
  right(rot);
}
moveForwardAndTurn(50, 90);

//loop over the same code n times
var n = 5;
while(n > 0) {
  n = n - 1;
  console.log('memememememememe');
}

// this infinite loop will crash:
var n = 5;
while(n > 0) {
  console.lag('memememememememe');
}

// this is a shortcut for loops.
// it's harder to cause an infinite loop
// this way. it uses the form:
// for(initializer; condition; incrementer)
for(var i = 0; i < 4; i++) {
  forward(50);
  right(90);
}

// this is a recursive function.
// it calls itself, which calls itself again.
// also capable of crashing if done wrong.
function abacabadabacaba (letters, depth) {

  // if not provided with a depth argument,
  // default to zero.
  if(depth === undefined) depth = 0;

  var newDepth = depth+1;
  var letter =
    letters[letters.length-newDepth];

  if(newDepth == letters.length) {

  	// we are at our last step,
    // so don't recurse any more.
    return letter;
  } else {

  	// we need to go deeper
    var eitherSide =
      abacabadabacaba(letters, newDepth);
    return eitherSide + letter + eitherSide;
  }
}

// to log 'abacabadabacaba':
console.log(abacabadabacaba(
  ['a', 'b', 'c', 'd']
));

//guess what this will do?
console.log(abacabadabacaba(
  ['a', 'b', 'c', 'd', 'f']
));

// this is a string of characters
var greeting = 'Hello World!';

// HELLO WORLD!
var entusiasticGreeting =
  greeting.toUpperCase();

// these are number
var coolnessAmount = -5;
var pi = 3.14;

// to increase your coolness,
// you can assign it a new value
coolnessAmount = (coolnessAmount + 3);

// this is a shortcut for the same statement
coolnessAmount += 3;

// testing whether things are equal is
// different from assigning a value.
// the following will run, but it will
// assign 3 instead of testing for 3
if(coolnessAmount = 3) {
  ...
}

//you really want:
if(coolnessAmount == 3) {

}

// this is an Array
var shoppingList = [
  'apples',
  'oranges',
  'bananas'
];
var emptyList = [];
var otherEmptyList = new Array();

// this is an object:
var sonic = {
  speed: Infinity,
  rings: 1,
  increaseSpeed: function(amount) {
    this.speed += amount;
  }
};

//you can get and set most object properties.
sonic.rings = 4;
console.log('sonic is going '
    + sonic.speed + ' miles per hour with '
    + sonic.rings + ' rings');

//even functions can be treated like values.
//and the functions 'remember' the state of
//outside variables when they were created.
//this is one of javascript's core features.
var speedMultiplier = 5;
sonic.increaseSpeed = function (amount) {
  this.speed += amount * speedMultiplier;
}