Same gravity as JetpackJoyride

You may know JetpackJoyride : http://halfbrick.com/our-games/jetpack-joyride/

I'm wondering how is the gravity handled. Does this use real physics, or do they change the velocity manually?

I personally made a similar 2D game, and I don't have the same effect. I set the gravity scale of my rigidbody to 1.2, and this is what I do when the user touch the screen:

 void FixedUpdate () {
         rigidBody.velocity = new Vector2 (rigidBody.velocity.x + 0.002f, rigidBody.velocity.y); // move forward with acceleration
         if (touching) {
             rigidBody.AddForce (new Vector2(0, 30));
         }
     }

Unfortunately, my character has alot of inertia and is not as reactive as the jetpack joyrider. I tried playing with gravity and AddForce, but I get nothing really playable.