title: Making a sprite move based on its rotation
body: <p>I am new to Unity2D and I am trying to get my sprite to move based on the direction it is facing.  I was able to get the rotation based on pressing A or the D key but when it comes to moving forward based on which direction my sprite is facing I am running into errors</p>
  
  <p>My current code :</p>
  
  <pre><code>#pragma strict
  
  var moveForward : KeyCode;
  var turnRight : KeyCode;
  var turnLeft : KeyCode;
  var fire : KeyCode;
  
  var speed : float = 4;
  var turnSpeed : float = 2;
  
  function Update () {
  
  // When the user wants to jet pulse forward.
  if(Input.GetKey(moveForward)){
  
      // NEEDS FIXING HERE!!! &lt;&lt;&lt;&lt;&lt;
      rigidbody2D.velocity.x = Mathf.Cos(rigidbody2D.rotation) * speed;
      rigidbody2D.velocity.y = Mathf.Sin(rigidbody2D.rotation) * speed;
  
  }
  
  // When we rotate the sprite.
  if(Input.GetKey(turnRight)){
  
      transform.Rotate(0.0f, 0.0f, -5.0f);
  
  }else if(Input.GetKey(turnLeft)){
  
      transform.Rotate(0.0f, 0.0f, 5.0f);
  
  }
  }
  </code></pre>