createCanvas(400, 400);

  /*

  planck.testbed(function(testbed) {

    var world = planck.World();

    // rest of your code

    return world; // make sure you return the world

  });

  */

  // This is a fun demo that shows off the wheel joint

planck.testbed('Car', function(testbed) {

  testbed.speed = 1.3;

  testbed.hz = 50;

​

  var pl = planck, Vec2 = pl.Vec2;

  var world = new pl.World({

    gravity : Vec2(0, -10)

  });

​

  // wheel spring settings

  var HZ = 4.0;

  var ZETA = 0.7;

  var SPEED = 50.0;

​

  var ground = world.createBody();

​

  var groundFD = {

    density : 0.0,

    friction : 0.6

  };

​

  ground.createFixture(pl.Edge(Vec2(-20.0, 0.0), Vec2(20.0, 0.0)), groundFD);

​

  var hs = [ 0.25, 1.0, 4.0, 0.0, 0.0, -1.0, -2.0, -2.0, -1.25, 0.0 ];

​

  var x = 20.0, y1 = 0.0, dx = 5.0;

​

  for (var i = 0; i < 10; ++i) {

    var y2 = hs[i];

    ground.createFixture(pl.Edge(Vec2(x, y1), Vec2(x + dx, y2)), groundFD);

    y1 = y2;

    x += dx;

  }

​

  for (var i = 0; i < 10; ++i) {

    var y2 = hs[i];

    ground.createFixture(pl.Edge(Vec2(x, y1), Vec2(x + dx, y2)), groundFD);

    y1 = y2;

    x += dx;

  }

​

  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 40.0, 0.0)), groundFD);

​

  x += 80.0;

  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 40.0, 0.0)), groundFD);

​

  x += 40.0;

  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 10.0, 5.0)), groundFD);

​

  x += 20.0;

  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x + 40.0, 0.0)), groundFD);

​

  x += 40.0;

  ground.createFixture(pl.Edge(Vec2(x, 0.0), Vec2(x, 20.0)), groundFD);

​

  // Teeter

  var teeter = world.createDynamicBody(Vec2(140.0, 1.0));

  teeter.createFixture(pl.Box(10.0, 0.25), 1.0);

  world.createJoint(pl.RevoluteJoint({

    lowerAngle : -8.0 * Math.PI / 180.0,

    upperAngle : 8.0 * Math.PI / 180.0,

    enableLimit : true

  }, ground, teeter, teeter.getPosition()));

​

  teeter.applyAngularImpulse(100.0, true);

​

  // Bridge

  var bridgeFD = {};

  bridgeFD.density = 1.0;

  bridgeFD.friction = 0.6;

​

  var prevBody = ground;

  for (var i = 0; i < 20; ++i) {

    var bridgeBlock = world.createDynamicBody(Vec2(161.0 + 2.0 * i, -0.125));

    bridgeBlock.createFixture(pl.Box(1.0, 0.125), bridgeFD);

​

    world.createJoint(pl.RevoluteJoint({}, prevBody, bridgeBlock, Vec2(160.0 + 2.0 * i, -0.125)));

​

    prevBody = bridgeBlock;

  }

​

  world.createJoint(pl.RevoluteJoint({}, prevBody, ground, Vec2(160.0 + 2.0 * i, -0.125)));

​

  // Boxes

  var box = pl.Box(0.5, 0.5);

​

  world.createDynamicBody(Vec2(230.0, 0.5))

    .createFixture(box, 0.5);

​

  world.createDynamicBody(Vec2(230.0, 1.5))

    .createFixture(box, 0.5);

​

  world.createDynamicBody(Vec2(230.0, 2.5))

    .createFixture(box, 0.5);

​

  world.createDynamicBody(Vec2(230.0, 3.5))

    .createFixture(box, 0.5);

​

  world.createDynamicBody(Vec2(230.0, 4.5))

    .createFixture(box, 0.5);

​

  // Car

  var car = world.createDynamicBody(Vec2(0.0, 1.0));

  car.createFixture(pl.Polygon([

    Vec2(-1.5, -0.5),

    Vec2(1.5, -0.5),

    Vec2(1.5, 0.0),

    Vec2(0.0, 0.9),

    Vec2(-1.15, 0.9),

    Vec2(-1.5, 0.2)

  ]), 1.0);

​

  var wheelFD = {};

  wheelFD.density = 1.0;

  wheelFD.friction = 0.9;

​

  var wheelBack = world.createDynamicBody(Vec2(-1.0, 0.35));

  wheelBack.createFixture(pl.Circle(0.4), wheelFD);

​

  var wheelFront = world.createDynamicBody(Vec2(1.0, 0.4));

  wheelFront.createFixture(pl.Circle(0.4), wheelFD);

​

  var springBack = world.createJoint(pl.WheelJoint({

    motorSpeed : 0.0,

    maxMotorTorque : 20.0,

    enableMotor : true,

    frequencyHz : HZ,

    dampingRatio : ZETA

  }, car, wheelBack, wheelBack.getPosition(), Vec2(0.0, 1.0)));

​

  var springFront = world.createJoint(pl.WheelJoint({

    motorSpeed : 0.0,

    maxMotorTorque : 10.0,

    enableMotor : false,

    frequencyHz : HZ,

    dampingRatio : ZETA

  }, car, wheelFront, wheelFront.getPosition(), Vec2(0.0, 1.0)));

​

  testbed.keydown = function() {

    if (testbed.activeKeys.down) {

      HZ = Math.max(0.0, HZ - 1.0);

      springBack.setSpringFrequencyHz(HZ);

      springFront.setSpringFrequencyHz(HZ);

​

    } else if (testbed.activeKeys.up) {

      HZ += 1.0;

      springBack.setSpringFrequencyHz(HZ);

      springFront.setSpringFrequencyHz(HZ);

    }

  };

​

  testbed.step = function() {

    if (testbed.activeKeys.right && testbed.activeKeys.left) {

      springBack.setMotorSpeed(0);

      springBack.enableMotor(true);

​

    } else if (testbed.activeKeys.right) {

      springBack.setMotorSpeed(-SPEED);

      springBack.enableMotor(true);

​

    } else if (testbed.activeKeys.left) {

      springBack.setMotorSpeed(+SPEED);

      springBack.enableMotor(true);

​

    } else {

      springBack.setMotorSpeed(0);

      springBack.enableMotor(false);

    }

​

    var cp = car.getPosition();

    if (cp.x > testbed.x + 10) {

      testbed.x = cp.x - 10;

​

    } else if (cp.x < testbed.x - 10) {

      testbed.x = cp.x + 10;

    }

  };

​

  testbed.info('←/→: Accelerate car, ↑/↓: Change spring frequency');

​

  return world;

});

}

​

function draw() {

  background(220);

}