DragDrop

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

public class DragDrop : MonoBehaviour
{
    private Vector3 mOffset;
    public Vector3 cardPos; //Center of Play Area
    public Vector3 cardPosStatic; //Original position which should only change when a card is drawn
    private Vector3 cardPosLast;
    public bool playAllowed;
    private Vector3 setCardDepth;
    private float mZCoord;
    public bool castChecker;
    private bool firstClick;

    void Start()
    {
        setCardDepth = new Vector3(0,0,-5);
        cardPos = new Vector3(0,300,-5);
        cardPosLast = gameObject.transform.position;
    }

    private void OnCollisionEnter(Collision other)
    {
        if (other.gameObject.tag == "castArea")
        {
            playAllowed = true;
        }
    }

    private void OnCollisionExit (Collision other)
    {
        playAllowed = false;
    }

    public void ResetPos()
    {
        gameObject.transform.position = cardPosStatic;
        playAllowed = false;
        castChecker = false;
    }

    void OnMouseDown()
    {
        if (!firstClick)
        {
            cardPosStatic = gameObject.transform.position;
            firstClick = true;
        }
        cardPosLast = gameObject.transform.position;
        mZCoord = Camera.main.WorldToScreenPoint(gameObject.transform.position).z;
        // Store offset = gameobject world pos - mouse world pos
        mOffset = gameObject.transform.position - GetMouseAsWorldPoint();
    }

    private Vector3 GetMouseAsWorldPoint()
    {
        // Pixel coordinates of mouse (x,y)
        Vector3 mousePoint = Input.mousePosition;
        // z coordinate of game object on screen
        mousePoint.z = mZCoord;
        // Convert it to world points
        return Camera.main.ScreenToWorldPoint(mousePoint);
    }

    void OnMouseDrag()
    {
            transform.position = (GetMouseAsWorldPoint() + mOffset) + setCardDepth;
    }

    void OnMouseUp()
    {
        if (playAllowed)
        {
            gameObject.transform.position = cardPos;
            castChecker = true;

        }
        if (playAllowed == false)
        {
            ResetPos();
        }
    }
}