Basic movement script

Hi, I have a basic movement script (The game is a 2D platform style game). The character is continuously swimming forwards, to control it you rotate it up and down to move up and down.

The problem I am having is, when it rotates, it stops the transform.velocity until it stops rotating, How could I do this more smoothly?

I have tried both
transform.Rotate(0,0,2)
and
transform.Rotate(Vector3.forward * 2,Space.Self)


My code is

Code (csharp):

1. public static var spinSpeed : float = 1.5; //speed which the object will spin
2. public static var forwardVelocityValue : float = 4; //speed the object will move forward
3. var heroObject : GameObject; //the object this script applies to
4. var maximumUpRotation : float = 80;//The maximum rotation for the Up button to work
5. var minimumUpRotation : float = 275;//The minimum rotation for the Up button to work
6. var maximumDownRotation : float = 280;//The maximum rotation for the Down button to work
7. var minimumDownRotation : float = 85;//The minimum rotation for the Down button to work
8. var upButtonX = Screen.width/4 * 3;
9.  
10. var Alive : boolean = true;
11. var getHealth : PlayerHealth;
12.  
13. function Start()
14. {
15.     getHealth = GameObject.Find("Player").GetComponent(PlayerHealth);
16. }
17.  
18. function OnGUI ()
19. {
20.     if (GUI.RepeatButton (Rect (Screen.width/8*6.5,Screen.height/8*6,Screen.width/100*15,Screen.height/100*20), "Up")) //spin up button
21.     {
22.         if (Alive == true)
23.         {
24.             if (transform.localEulerAngles.z < maximumUpRotation) //if rotation is 80 or less then do
25.             {
26.                 heroObject.transform.Rotate(Vector3.forward * spinSpeed,Space.Self);//Object to spin.Startspinning.angle.z
27.             }    
28.             if (transform.localEulerAngles.z > minimumUpRotation) //if rotation is 255 or more then do
29.             {
30.                 heroObject.transform.Rotate(0,0,spinSpeed);//Object to spin.Startspinning.angle.z
31.             }
32.         }    
33.     }
34.  
35.     if (GUI.RepeatButton (Rect (Screen.width/8*.5,Screen.height/8*6,Screen.width/100*15,Screen.height/100*20), "Down"))//spin down button
36.     {
37.         if (Alive == true)
38.         {
39.             if (transform.localEulerAngles.z < minimumDownRotation) //if rotation is 85 or less then do
40.             {
41.                 heroObject.transform.Rotate(0,0,-spinSpeed);//Object to spin.Startspinning.angle.-z
42.                
43.             }
44.             if (transform.localEulerAngles.z > maximumDownRotation) //if rotation is 250 or more then do
45.             {
46.                 heroObject.transform.Rotate(0,0,-spinSpeed);//Object to spin.Startspinning.angle.-z
47.             }
48.         }
49.     }
50. }
51.  
52.  
53. function FixedUpdate()
54. {
55.     if (getHealth.health == 0)
56.     {
57.         Alive = false;
58.     }
59.     if (Alive == true)
60.     {
61.         rigidbody2D.velocity = transform.right * forwardVelocityValue;//object to move.velocity = speed (x,y)
62.     }
63.     if (Alive == false)
64.     {
65.         rigidbody2D.velocity = transform.up * 2;//object to move.velocity = speed (x,y)
66.     }
67.    
68. }