Move player forward relative to direction (pointing towards) using touch input

Hello -

Continuing to port my first game to Unity, I've noticed that many tutorials are based on the use of the computer keyboard and not touch input from a mobile device. That has stalled me a bit, since I am using touch input.

That said, I have a script for the buttons and a script for the player controller. I am convinced the script for the button works fine, but am stuck with the player controller. This is what I have in the player controller script thus far:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class PlayerShipControl : MonoBehaviour {
5.  
6.     public float rotationspeed = 5f;
7.     private Rigidbody2D rb;
8.  
9.  
10.     // Use this for initialization
11.     void Start () {
12.         rb = GetComponent<Rigidbody2D> ();
13.     }
14.    
15.     // Update is called once per frame
16.     void Update () {
17.  
18.         if (TouchJoyPad.Button01) {
19.             transform.Rotate (0, 0, rotationspeed);
20.         }
21.         if (TouchJoyPad.Button02) {
22.             transform.Rotate (0, 0, rotationspeed * -1);
23.         }
24.         if (TouchJoyPad.Button03) {
25.             //insert code to move forward
26.         }
27.     }
28. }

I know I must create a variable to assign a speed. Ideally I should accelerate to a certain max speed when touch is pressed, and coast and stop when touch is released.

My object PlayerShip starts pointing up. How do I know its direction and how do I accelerate relative to its direction?

Thanks, regards,
Marcos

 

If it helps:

My PlayerShip faces up, and rotates on its Z axis. Thus it's not a top-down, but a front-facing scene.