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

public class Player : MonoBehaviour
{
    Vector3 playerPosition;
    Vector3 mouseF;
    Vector3 mouseN;

    void FixedUpdate()
    {
        if (Input.GetMouseButton(0))
        {
            setMouseF();
            setMouseN();

            Debug.DrawRay(mouseN, mouseF - mouseN, Color.green);
            Debug.DrawRay(mouseN, (playerPosition - mouseN), Color.red);

            // move the player base on mouse position
            transform.position = mouseF;
        }

        if (Input.GetMouseButtonUp(0))
        {

            // on mouse release, set the new player position
            playerPosition = mouseF;
        }

    }

    void setMouseF()
    {
        Vector3 mouseFar = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 10f);
        mouseF = Camera.main.ScreenToWorldPoint(mouseFar);
    }

    void setMouseN()
    {
        Vector3 mouseNear = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.nearClipPlane);
        mouseN = Camera.main.ScreenToWorldPoint(mouseNear);
    }
}

Vector3 initialMousePos;
Vector3 offset;

private void Update() {
    if(Input.GetMouseButtonDown(0))
    {
        initialMousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
    }
    if(Input.GetMouseButton(0))
    {
        offset = initialMousePos - Camera.main.ScreenToWorldPoint(Input.mousePosition);
        transform.position += offset;
    }
}

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

public class Player : MonoBehaviour
{
    Vector3 playerPosition;
    Vector3 mouseF;
    Vector3 mouseN;
    Vector3 diff;

    void FixedUpdate()
    {
        if (Input.GetMouseButtonDown(0))
        {
            InitPlayer();
        }

        if (Input.GetMouseButton(0))
        {
            SetMouseF();
            SetMouseN();

            Debug.DrawRay(mouseN, mouseF - mouseN, Color.green);
            Debug.DrawRay(mouseN, (mouseF + diff) - mouseN, Color.red);

            // move the player base on mouse position
            transform.position = mouseF + diff;
        }

        if (Input.GetMouseButtonUp(0))
        {
        }

    }

    void InitPlayer()
    {
        SetMouseF();

        // set player position where the object is
        playerPosition = transform.position;

        // get the distance between the player and mouse click
        diff = playerPosition - mouseF;
    }

    void SetMouseF()
    {
        Vector3 mouseFar = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 10f);
        mouseF = Camera.main.ScreenToWorldPoint(mouseFar);
    }

    void SetMouseN()
    {
        Vector3 mouseNear = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.nearClipPlane);
        mouseN = Camera.main.ScreenToWorldPoint(mouseNear);
    }
}