gimm-platformer-project/Assets/Scripts/GroundCheck.cs

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

public class GroundCheck : MonoBehaviour
{
    GameObject Player;
    private LayerMask solidLayer;

    private void Start()
    {
        Player = gameObject.transform.parent.gameObject;
        solidLayer = LayerMask.GetMask("SolidObject");
    }
    private void OnCollisionEnter2D(Collision2D collision)
    {
        if (collision.collider.tag == "Ground" || collision.collider.tag == "Platform" || collision.collider.tag == "Tetromino")
        {
            Debug.Log("Now standing on "+ collision.collider.name);
            Player.GetComponent<Movement2D>().isGrounded = true;
        }
    }

    private void OnCollisionExit2D(Collision2D collision)
    {
        if (collision.collider.tag == "Ground" || collision.collider.tag == "Platform" || collision.collider.tag == "Tetromino")
        {
            if (GetComponent<BoxCollider2D>().IsTouchingLayers(solidLayer) == false)
            {
                Debug.Log("No longer standing on " + collision.collider.name);
                Player.GetComponent<Movement2D>().isGrounded = false;
            }
        }
    }
}