Collision with a group not working

[Decktonic]

Hi, I'm building a little game where a ship is contained within a square in the middle of the game world and "bounces" off the walls. It's easier to just see it in action so here's what I have so far: 

http://mappdev.com/spin/

The ship starts in the middle of the canvas, spinning endlessly. When you click or touch the canvas, the ship moves forward in the angle it's facing. 

So I have a 640x960 canvas with a red background and then I draw a black 600x600 rounded rectangle in the center, then I add 4 objects on top, bottom and sides that are the "walls" meant to keep the ship within the square. I'm using a group for these walls. 

Right now the ship bounces off the edges of the game world but as far as I can tell it doesn't collide with the walls at all. 

Here's my code: 

var defaults = { 
  canvasWidth: 640, 
  canvasHeight: 960, 
  angle: -90, 
  velocity: 500, 
  angularVelocity: 400, 
}; 

var game = new Phaser.Game(defaults.canvasWidth, defaults.canvasHeight, Phaser.AUTO, 'container', { preload: preload, create: create, update: update, render: render });
var walls; 
var ship; 

function preload() {

  game.scale.scaleMode = Phaser.ScaleManager.SHOW_ALL;

  game.load.image('wall', 'assets/wall.png'); 
  game.load.image('ship', 'assets/ship.png'); 
  game.load.image('coin', 'assets/coin.png'); 
  game.load.image('bomb', 'assets/bomb.png');

}

function create() {

  game.physics.startSystem(Phaser.Physics.ARCADE); 

  game.stage.backgroundColor = "#FF0000"; // "#37474F";

  var graphics = game.add.graphics(20, 180);
  graphics.beginFill(0x000000, 1);
  graphics.drawRoundedRect(0, 0, 600, 600, 8);

  walls = game.add.physicsGroup(); 

  wall_top = walls.create(0, 0, 'wall'); 
  wall_top.scale.setTo(640, 180); 
  wall_top.body.immovable = true; 

  wall_right = walls.create(620, 180, 'wall'); 
  wall_right.scale.setTo(20, 600); 
  wall_right.body.immovable = true; 

  wall_bottom = walls.create(0, 780, 'wall'); 
  wall_bottom.scale.setTo(640, 180); 
  wall_bottom.body.immovable = true; 

  wall_left = walls.create(0, 180, 'wall'); 
  wall_left.scale.setTo(20, 600); 
  wall_left.body.immovable = true; 

  ship = game.add.sprite(defaults.canvasWidth * 0.5, defaults.canvasHeight * 0.5, 'ship'); 
  ship.scale.setTo(0.5, 0.5); 
  ship.anchor.set(0.5, 0.5); 
  ship.angle = defaults.angle; 

  game.physics.arcade.enable(ship); 

  ship.body.allowGravity = false; 
  ship.body.immovable = true; 
  ship.body.collideWorldBounds = true; 
  ship.body.bounce.setTo(1, 1); 
  ship.body.angularVelocity = defaults.angularVelocity; 

}

function update() {

  game.physics.arcade.collide(ship, walls);

  if(game.input.activePointer.isDown) { 
    ship.body.angularVelocity = 0; 
    ship.body.velocity.copyFrom(game.physics.arcade.velocityFromAngle(ship.angle, defaults.velocity));
  }
  else { 
    ship.body.angularVelocity = defaults.angularVelocity; 
    ship.body.velocity.set(0, 0); 
  }

  if(ship.body.blocked.up || ship.body.blocked.down || ship.body.touching.up || ship.body.touching.down) { 
    ship.angle = 0 - ship.angle; 
    ship.body.velocity.copyFrom(game.physics.arcade.velocityFromAngle(ship.angle, defaults.velocity));
  }
  if(ship.body.blocked.right || ship.body.blocked.left || ship.body.touching.right || ship.body.touching.left) { 
    ship.angle = 180 - ship.angle; 
    ship.body.velocity.copyFrom(game.physics.arcade.velocityFromAngle(ship.angle, defaults.velocity));
  }

}

function render() { 

  // game.debug.spriteInfo(ship, 32, 32); 

}

Any idea what I'm missing? I'm using latest Phaser version 2.4.4 by the way. 

[Decktonic]

OK rich provided the fix via Slack: 

Quote

two immovable objects cannot collide, most likely your ship didn’t ought to be immovable

Removing this line: 

ship.body.immovable = true;

Fixed it!