Fire JS Bin - TurtleGraphicsExplorer

var ANIMATION;
var CTX;
var CANVAS;
var CANVAS_WIDTH;
var CANVAS_HEIGHT;
var DEFAULT_BG;
var DEFAULT_FG;
var BG;
var FG;
var XCOR;
var YCOR;
var ROTATION;
var PEN_DOWN;
var PI = Math.PI;
var DEG2RAD = PI / 180;
var RAD2DEG = 180 / PI;
var FORWARD_FAILED;
var FILL = "";
var MODE = "immediate";
var FOOD_X = 0;
var FOOD_Y = 0;
var DISTANCE_TO_FOOD;
var DISTANCE_LAST_TIME;
var OVERLAY;
var OVERLAY_CTX;
var TURTLE_IMG;
var TURTLE_IMG_SRC = "/assets/turtle.png";
var TURTLE_WIDTH;
var TURTLE_HEIGHT;
var TURTLE_LOADED = false;
var TURTLE_VISIBLE = true;

function RESET_CANVAS(a) {
  a.setTransform(1, 0, 0, 1, 0, 0);
  a.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT)
}
function RESET() {
  RESET_CANVAS(CTX);
  CTX.fillStyle = DEFAULT_BG;
  CTX.strokeStyle = DEFAULT_FG;
  CTX.fillRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);
  STOP_ANIM();
  XCOR = CANVAS_WIDTH / 2;
  YCOR = CANVAS_HEIGHT / 2;
  ROTATION = 0;
  PEN_DOWN = true;
  MODE = "immediate";
  TURTLE_VISIBLE = true;
  CTX.translate(XCOR, YCOR);
  RESET_CANVAS(OVERLAY_CTX);
  DRAW_TURTLE()
}
function GET_CANVAS_POS() {
  var b = CANVAS;
  var c = 0,
      a = 0;
  if (b.offsetParent) {
    do {
      c += b.offsetLeft;
      a += b.offsetTop
    } while (b = b.offsetParent)
  }
  return [c, a]
}
function INIT(b, c, a) {
  if (typeof b === "string") {
    CANVAS = document.getElementById(b)
  }
  if (CANVAS.getContext) {
    CTX = CANVAS.getContext("2d")
  } else {
    return
  }
  CANVAS_WIDTH = CANVAS.width;
  CANVAS_HEIGHT = CANVAS.height;
  var d = GET_CANVAS_POS();
  OVERLAY = CANVAS.cloneNode(false);
  OVERLAY.setAttribute("id", "overlay");
  OVERLAY.style.zIndex = "100";
  OVERLAY.style.position = "absolute";
  OVERLAY.style.left = d[0] + "px";
  OVERLAY.style.top = d[1] + "px";
  CANVAS.parentNode.insertBefore(OVERLAY, CANVAS);
  OVERLAY_CTX = OVERLAY.getContext("2d");
  LOAD_TURTLE(TURTLE_IMG_SRC);
  BG = DEFAULT_BG = c || "#000000";
  FG = DEFAULT_FG = a || "#00FF00";
  CTX.save();
  RESET()
}
function LOAD_TURTLE(a) {
  TURTLE_IMG = new Image();
  TURTLE_IMG.onload = function () {
    TURTLE_WIDTH = TURTLE_IMG.width;
    TURTLE_HEIGHT = TURTLE_IMG.height;
    TURTLE_LOADED = true;
    DRAW_TURTLE()
  };
  TURTLE_IMG.src = a
}
function FORWARD(a) {
  if (MODE == "immediate") {
    CTX.beginPath();
    CTX.moveTo(0, 0)
  }
  if (PEN_DOWN) {
    CTX.lineTo(0, -a);
    CTX.translate(0, -a);
    if (MODE == "immediate") {
      CTX.stroke()
    }
  } else {
    CTX.moveTo(0, -a);
    CTX.translate(0, -a)
  }
  XCOR += a * Math.cos(BEARING() * Math.PI / 180);
  YCOR += a * Math.sin(BEARING() * Math.PI / 180);
  if (TURTLE_VISIBLE) {
    DRAW_TURTLE()
  }
}
function BACK(a) {
  FORWARD(-a)
}
function RIGHT(a) {
  ROTATION -= a;
  ROTATION %= 360;
  CTX.rotate(a * Math.PI / 180);
  if (TURTLE_VISIBLE) {
    DRAW_TURTLE()
  }
}
function LEFT(a) {
  RIGHT(-a)
}
function REPEAT(d, c, a) {
  for (var b = 0; b < d; b++) {
    c.apply(this, a || [])
  }
}
function BEARING() {
  return ROTATION + 90
}
function PENDOWN() {
  PEN_DOWN = true;
  if (MODE == "delayed") {
    CTX.beginPath();
    CTX.moveTo(0, 0)
  }
}
function PENUP() {
  PEN_DOWN = false
}
function OUT_OF_BOUNDS() {
  if (XCOR < 0 || XCOR >= CANVAS_WIDTH) {
    return true
  } else {
    if (YCOR < 0 || YCOR >= CANVAS_HEIGHT) {
      return true
    } else {
      return false
    }
  }
}
function MOVE_FORWARD(a) {
  PENUP();
  FORWARD(a);
  PENDOWN()
}
function CHECK_FORWARD(a) {
  PENUP();
  FORWARD(a);
  FORWARD_FAILED = OUT_OF_BOUNDS();
  BACK(a);
  if (!FORWARD_FAILED) {
    PENDOWN();
    FORWARD(a)
  }
  PENDOWN()
}
function STUCK() {
  return FORWARD_FAILED
}
function SET_BG(a) {
  BG = a
}
function SET_LINE(a) {
  FG = a;
  CTX.strokeStyle = FG
}
function BEGIN_FILL(a) {
  FILL = a;
  CTX.fillStyle = FILL;
  MODE = "delayed";
  PENDOWN()
}
function END_FILL() {
  CTX.fill();
  CTX.stroke();
  MODE = "immediate";
  FILL = ""
}
function CENTER_X() {
  return CANVAS_WIDTH / 2
}
function CENTER_Y() {
  return CANVAS_HEIGHT / 2
}
function GET_WIDTH() {
  return CANVAS_WIDTH
}
function GET_HEIGHT() {
  return CANVAS_HEIGHT
}
function SET_FOOD(a, b) {
  FOOD_X = a;
  FOOD_Y = b
}
function DIST(b, d, a, c) {
  return Math.sqrt(Math.pow(a - b, 2) + Math.pow(c - d, 2))
}
function SMELL() {
  var a;
  DISTANCE_TO_FOOD = DIST(FOOD_X, FOOD_Y, XCOR, YCOR);
  if (DISTANCE_LAST_TIME === undefined) {
    DISTANCE_LAST_TIME = DISTANCE_TO_FOOD
  }
  if (DISTANCE_TO_FOOD > DISTANCE_LAST_TIME) {
    a = "weaker"
  } else {
    a = "stronger"
  }
  DISTANCE_LAST_TIME = DISTANCE_TO_FOOD;
  return a
}
function STOP_ANIM() {
  if (ANIMATION) {
    clearInterval(ANIMATION)
  }
}
function ANIMATE(b, a) {
  function c(d) {
    d = d || 1;
    b.call();
    if (a && d < a) {
      setTimeout(function () {
        c(++d)
      }, 25)
    } else {
      ANIMATION = setInterval(b, 25)
    }
  }
  c(1)
}
function RESET_OVERLAY() {
  OVERLAY_CTX.save();
  OVERLAY_CTX.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);
  OVERLAY_CTX.setTransform(1, 0, 0, 1, 0, 0)
}
function DRAW_TURTLE() {
  RESET_OVERLAY();
  if (TURTLE_LOADED) {
    OVERLAY_CTX.translate(XCOR, CANVAS_HEIGHT - YCOR);
    OVERLAY_CTX.rotate(-ROTATION * Math.PI / 180);
    OVERLAY_CTX.drawImage(TURTLE_IMG, -TURTLE_WIDTH / 2, -TURTLE_HEIGHT / 2, TURTLE_WIDTH, TURTLE_HEIGHT)
  }
  OVERLAY_CTX.restore()
}
function HIDE_TURTLE() {
  RESET_OVERLAY();
  TURTLE_VISIBLE = false
}
function SHOW_TURTLE() {
  TURTLE_VISIBLE = true;
  DRAW_TURTLE()
};

function SQUAREPIECE(a) {
  FORWARD(a);
  RIGHT(90)
}
function SQUARE(a) {
  REPEAT(4, SQUAREPIECE, [a])
}
function RECTANGLE(b, a) {
  REPEAT(2, function () {
    SQUAREPIECE(b);
    SQUAREPIECE(a)
  })
}
function TRIANGLE(a) {
  REPEAT(3, function () {
    FORWARD(a);
    RIGHT(120)
  })
}
function HOUSE(a) {
  SQUARE(a);
  FORWARD(a);
  RIGHT(30);
  TRIANGLE(a)
}
function THING() {
  FORWARD(100);
  RIGHT(90);
  FORWARD(100);
  RIGHT(90);
  FORWARD(50);
  RIGHT(90);
  FORWARD(50);
  RIGHT(90);
  FORWARD(100);
  RIGHT(90);
  FORWARD(25);
  RIGHT(90);
  FORWARD(25);
  RIGHT(90);
  FORWARD(50)
}
function CIRCLE(a) {
  REPEAT(360, function () {
    FORWARD(a);
    RIGHT(1)
  })
}
function ARCR(b, a) {
  REPEAT(a, function () {
    FORWARD(b);
    RIGHT(1)
  })
}
function ARCL(b, a) {
  REPEAT(a, function () {
    FORWARD(b);
    LEFT(1)
  })
}
function PETAL(a) {
  ARCR(a, 60);
  RIGHT(120);
  ARCR(a, 60);
  RIGHT(120)
}
function FLOWER(a) {
  REPEAT(6, function () {
    PETAL(a);
    RIGHT(60)
  })
}
function RAY(a) {
  REPEAT(2, function () {
    ARCL(a, 90);
    ARCR(a, 90)
  })
}
function SUN(a) {
  REPEAT(9, function () {
    RAY(a);
    RIGHT(160)
  })
}
function POLY(a, b) {
  REPEAT(360, function () {
    FORWARD(a);
    RIGHT(b)
  })
}
function NEWPOLY(a, b) {
  REPEAT(100, function () {
    FORWARD(a);
    RIGHT(b);
    FORWARD(a);
    RIGHT(2 * b)
  })
}
function POLYSPI(a, c, b) {
  if (b === undefined) {
    b = 1
  }
  FORWARD(a);
  RIGHT(c);
  if (a < 500) {
    POLYSPI(a + b, c, b)
  }
}
function MULTISPI(c, d, b, a) {
  if (a === undefined) {
    a = 1
  } else {
    a += 1
  }
  FORWARD(c);
  RIGHT(d);
  if (a < 500) {
    MULTISPI(c * b, d, b, a)
  }
}
function INSPI(b, d, c, a) {
  a = (a === undefined) ? 1 : a;
  FORWARD(b);
  RIGHT(d);
  if (a < 500) {
    INSPI(b, d + c, c, a)
  }
}
function SUBSPIRO(b, d, a) {
  var c = 1;
  while (c <= a) {
    FORWARD(b * c);
    RIGHT(d);
    c++
  }
}
function SPIRO(b, c, a) {
  REPEAT(100, SUBSPIRO, [b, c, a, 0])
}
function SUBGSPIRO(b, e, a, d) {
  var c = 1;
  while (c <= a) {
    FORWARD(b * c);
    if (d.indexOf(c) > -1) {
      LEFT(e)
    } else {
      RIGHT(e)
    }
    c++
  }
}
function GSPIRO(b, d, a, c) {
  REPEAT(100, SUBGSPIRO, [b, d, a, c])
}
function RAND(b, a) {
  return b + Math.random() * (a - b)
}
function RANDOM_MOVE(d, c, b, a, e) {
  REPEAT(e || 1000, function () {
    FORWARD(RAND(d, c));
    RIGHT(RAND(b, a))
  })
}
function RANDOM_MOVE_IN_BOX(d, c, b, a, e) {
  REPEAT(e || 1000, function () {
    RIGHT(RAND(b, a));
    CHECK_FORWARD(RAND(d, c));
    if (STUCK()) {
      RIGHT(180)
    }
  })
}
function RANDOM_COLOR() {
  var c = "0123456789ABCDEF";
  var a = "";
  for (var b = 0; b < 6; b++) {
    a += c.charAt(Math.round(Math.random() * 15))
  }
  return "#" + a
}
function FIND_BY_SMELL1() {
  ANIMATE(function () {
    FORWARD(1);
    if (SMELL() == "weaker") {
      RIGHT(1)
    }
  })
}
function FIND_BY_SMELL2(a) {
  ANIMATE(function () {
    FORWARD(1);
    if (SMELL() == "weaker") {
      RIGHT(a)
    }
  })
};
var feedback = document.getElementById("feedback");
var buffer = document.getElementById("turtle_buffer");

function RUN() {
  var buftext = buffer.value;
  feedback.innerText = "";
  try {
    eval(buftext)
  } catch (e) {
    feedback.innerText = e.message
  }
}
INIT("canvas", "#000000", "#FFFF00");

<!DOCTYPE HTML> 
<html>
  <head>
    <title>Turtle Graphics Explorer</title>
  </head>
  <body bgcolor="white">
    <table style="margin:0;padding:0" width="100%" height="100%" cellpadding="0" cellspacing="0">
      <tr>
        <td width="600" height="600" valign="top">
          <canvas id="canvas" width="600" height="600">Your browser does not support canvas.</canvas>
        </td>
        <td valign="top">
          <h3 id="title">Turtle Shell:</h3>
          <h4 id="subtitle"> a turtle graphics explorer.</h4>
          <form style="width: 100%; height: 90%;">
            <textarea id="turtle_buffer"> 
//use valid javascript and procedures below, then click 'RUN'
//eg:
HIDE_TURTLE();//speedup rendering
REPEAT(50, function(){
    SET_LINE(RANDOM_COLOR());
    RANDOM_MOVE_IN_BOX(RAND(-10,10), RAND(-10, 10), RAND(-90, 90), RAND(-90, 90));
});
SHOW_TURTLE();
/* PROCEDURES...
FORWARD(len);
BACK(len);
RIGHT(angle);
LEFT(angle);
REPEAT(times, fn, args);
PENDOWN();
PENUP();
HIDE_TURTLE();
SHOW_TURTLE();
RESET();
SQUAREPIECE(size);
SQUARE(size);
RECTANGLE(side1, side2);
TRIANGLE(size);
HOUSE(size);
THING();
CIRCLE(size);
ARCR(r, deg);
ARCL(r, deg);
PETAL(size);
FLOWER(size);
RAY(r);
SUN(size);
POLY(side, angle);
NEWPOLY(side, angle);
POLYSPI(side, angle, inc);
MULTISPI(side, angle, factor, iter);
INSPI(side, angle, inc, iter);
SUBSPIRO(side, angle, max);
SPIRO(side, angle, max);
SUBGSPIRO(side, angle, max, list);
GSPIRO(side, angle, max, list);
RAND(min, max);
RANDOM_MOVE(d1, d2, a1, a2, times);
RANDOM_MOVE_IN_BOX(d1, d2, a1, a2, times);
SET_BG(color);
SET_LINE(color);
BEGIN_FILL(color);
END_FILL();
SET_FOOD(x, y);
SMELL();
ANIMATE(fn, max);
STOP_ANIM();
FIND_BY_SMELL1();
FIND_BY_SMELL2(TURN);
 
SOURCE: http://github.com/bigfish/turtle
*/