One Way Platform Code

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

public class DropDown : MonoBehaviour
{
    public string oneWayPlatformLayerName = "OneWayPlatform";
    public string playerLayerName = "Player";

    private void Update()
    {
        if (Input.GetAxis("Vertical") < 0)
        {
            Physics2D.IgnoreLayerCollision(LayerMask.NameToLayer(playerLayerName), LayerMask.NameToLayer(oneWayPlatformLayerName), true);
        }
        else
        {
            Physics2D.IgnoreLayerCollision(LayerMask.NameToLayer(playerLayerName), LayerMask.NameToLayer(oneWayPlatformLayerName), false);
        }
    }
}