RPG Top Down / Isometric Camera Controller in C# for Unity

IsometricCameraController.cs

// RPG Top Down / Isometric Camera Controller

// Tested on Unity 2018.3.0f1

// While using the setup suggested by 
// https://answers.unity.com/questions/12027/how-to-do-a-camera-that-is-top-downisometric.html
// I found no off the shelf camera controllers that worked as I would have liked
// This is for basic mouse control (Rotate, Pan, Zoom)

// Improvement suggestions left as exercise for the reader:
//
// * Replacing magic numbers with serialised floats
//   that could be modified in the editor
// * Include keyboard controls
// * Add tilting

// Attach this script to any GameeObject
// Make sure the Camera is tagged as "Main Camera" in the inspector

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

public class IsometricCameraController : MonoBehaviour
{
    private bool isRotating;
    private bool isPanning;
    private float velocity;
    private float zoomVelocity;

    private float deltaX = 0f;
    private float deltaY = 0f;

    void Update() {
        if (Input.GetMouseButton(1)) {
            isRotating = true;
            velocity = 0f;
        } else {
            isRotating = false;
        }

        if (Input.GetMouseButton(2)) {
            isPanning = true;
            deltaX = 0f;
            deltaY = 0f;
        } else {
            isPanning = false;
        }

        if (isRotating == true) {
            RotateCameraTarget();
        } else if (isPanning == true) {
            PanCameraTarget();
        }

        CalculateRotation();
        CalculateZoom();
        CalculatePan();
    }

    void CalculateRotation() {
        Vector3 rot = Camera.main.transform.parent.eulerAngles;
        rot.y += velocity;
        Camera.main.transform.parent.eulerAngles = rot;
        velocity = Mathf.Lerp(velocity, 0f, Time.deltaTime * 5f);
    }

    void CalculateZoom() {
        if (Camera.main.orthographicSize < 15f) {
            Camera.main.orthographicSize = 15f;
            zoomVelocity = 0f;
            return;
        }

        if (Camera.main.orthographicSize > 80f) {
            Camera.main.orthographicSize = 80f;
            zoomVelocity = 0f;
            return;
        }

        if (
            Camera.main.orthographicSize + zoomVelocity >= 15f &&
            Camera.main.orthographicSize + zoomVelocity <= 80f
        ) {
            Camera.main.orthographicSize += zoomVelocity;
        }

        zoomVelocity -= Input.GetAxis("Mouse ScrollWheel") * 2f;
        zoomVelocity = Mathf.Lerp(zoomVelocity, 0f, Time.deltaTime * 5f);
    }

    void CalculatePan() {
        if (deltaX < 0) {
            Camera.main.transform.parent.Translate(-deltaX, 0, deltaX);
        }

        if (deltaX > 0) {
            Camera.main.transform.parent.Translate(-deltaX, 0, deltaX);
        }

        if (deltaY < 0) {
            Camera.main.transform.parent.Translate(-deltaY, 0, -deltaY);
        }

        if (deltaY > 0) {
            Camera.main.transform.parent.Translate(-deltaY, 0, -deltaY);
        }

        deltaY = Mathf.Lerp(deltaY, 0f, Time.deltaTime * 5f);
        deltaX = Mathf.Lerp(deltaX, 0f, Time.deltaTime * 5f);
    }

    void RotateCameraTarget() {
        velocity += Input.GetAxis("Mouse X") * 3f;
    }

    void PanCameraTarget() {
        deltaX = Input.GetAxisRaw("Mouse X") * 3f;
        deltaY = Input.GetAxisRaw("Mouse Y") * 3f;
    }
}