PlayerController.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class BallController : MonoBehaviour {

	public float velocity = 1f;
	public GameObject particle;
	public Text scoreText;
	public GameObject ground;
	public Button button;

	private Rigidbody rb;
	private int score;

	private float x, y;

	void Start () {
		rb = GetComponent<Rigidbody> ();
	}

	void FixedUpdate () {
		Vector3 moviment;

		if (Input.touchCount > 0 && Input.GetTouch (0).phase == TouchPhase.Moved) {
			var touchDeltaPosition = Input.GetTouch (0).deltaPosition;

			x = Mathf.Min (Mathf.Max (-1.2f, touchDeltaPosition.x), 1.2f);
			y = Mathf.Min (Mathf.Max (-1.2f, touchDeltaPosition.y), 1.2f);
		
			moviment = new Vector3 (x * velocity, 0, y * velocity);
		} else {
			moviment = new Vector3 (Input.GetAxis ("Horizontal") * velocity, 0, Input.GetAxis ("Vertical") * velocity);
		}

		rb.AddForce (moviment);
	}

	void OnTriggerEnter(Collider other) {
		DestroyObstacle (other);
		UpdateScore ();
	}

	void DestroyObstacle(Collider obstacle) {
		Instantiate (particle, obstacle.transform.position, Quaternion.identity);
		Destroy (obstacle.gameObject);
	}

	void UpdateScore () {
		score++;
		scoreText.text = "Score: " + score.ToString();
	}
}