hey all.
i am new to scripting and i am making a game for mobile devices.
i have made a very basic ladder script with the help of youtube.
it works well with a standalone (using up and down arrows to move up and down the ladder) but i would like to put it into an android game so that when you touch a button you can go up it and when you let go of the button you fall back down.
my question is how would i rewrite the script to work with button touch, i have tried using getbuttondown instead of getkeydown but when i do this the character only moves a tiny bit and doesnt go up the ladder at all.
any help would be greatly appreciated 
this is my script
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Ladder : MonoBehaviour {
public float speed = 6;
// Use this for initialization
void Start () {
}
// Update is called once per frame
void Update () {
}
void OnTriggerStay2D(Collider2D other)
{
if (other.tag == "Player" && Input.GetKey (KeyCode.UpArrow)) {
other.GetComponent<Rigidbody2D> ().velocity = new Vector2 (0, speed);
} else if (other.tag == "Player" && Input.GetKey (KeyCode.DownArrow)) {
other.GetComponent<Rigidbody2D> ().velocity = new Vector2 (0, -speed);
} else
{
other.GetComponent<Rigidbody2D> ().velocity = new Vector2 (0, 1);
}
}
}