var jumpSpeed : float = 12.0;
var gravity : float = 20.0;

private var moveDirection : Vector3 = Vector3.zero;

function Update() {
    var controller : CharacterController = GetComponent(CharacterController);
    moveDirection = Vector3(0, jumpSpeed, 0);
    if (Input.GetButton ("Fire2")) {
        moveDirection.y += jumpSpeed;
    }

    moveDirection.y -= gravity * Time.deltaTime;

    controller.Move(moveDirection * Time.deltaTime);
}