How to make a slider menu

 using UnityEngine;
 using System.Collections;
 
 public class sliderThing: MonoBehaviour {
 
     // Use this for initialization
 
     public int menuOptions = 5;
     public int sliderSize = 100;
     public int menuDivisionSize;
     public int selectValue = 0;
     public int selectedOption;
 
     void Start () {
         menuDivisionSize = sliderSize/menuOptions;
 
     }
     
     // Update is called once per frame
     void Update () {
     
         if(Input.GetKey(KeyCode.D))
         {
             selectValue ++;
         }
         if(Input.GetKey(KeyCode.A))
         {
             selectValue --;
         }
         if(selectValue <0){selectValue = 0;}
         if(selectValue > sliderSize){selectValue = sliderSize;}
         for(int i = 0; i <= menuOptions; i++)
         {
 
             if(selectValue > i*menuDivisionSize && selectValue < (i+1)*menuDivisionSize)
             {
                 selectedOption = i;
             }
         }
     }
 }
 

this works, perhaps you can implement it into your game idea? variables are public because I like to see them in the editor for debugging :)