CameraController.cs

using UnityEngine;

public class CameraController : MonoBehaviour
{
    [Header("Camera Movement Options")]
    public float keyboardPanSpeed = 100f;
    public float mousePanSpeed = 50f;
    public float mousePanBaseSpeed = 0.01f;
    public float zoomSpeed = 50f;
    public float edgeSize = 20f;

    [Header("Camera Pan Boundaries")]
    public float minX = 0;
    public float maxX = 0;
    public float minY = 0;
    public float maxY = 0;
    public float minZ = 0;
    public float maxZ = 0;

    private bool movementEnabled = true;
    private Vector3 cameraStartPosition;

    void Start () {
        cameraStartPosition = transform.position;
    }

    void Update () {
        // Toggle movement on/off with Escape key:
        if (Input.GetKeyDown(KeyCode.Escape)) {
            movementEnabled = !movementEnabled;

            // Reset camera position when movement is disabled:
            if (!movementEnabled) {
                transform.position = cameraStartPosition;
            }
        }

        if (!movementEnabled) return;

        // Calculate pan/zoom from keyboard/controller axis:
        Vector3 keyboardTranslate = new Vector3(
            (Input.GetAxisRaw("Horizontal") * keyboardPanSpeed) * Time.deltaTime,
            -Input.GetAxisRaw("Mouse ScrollWheel") * zoomSpeed, 
            (Input.GetAxisRaw("Vertical") * keyboardPanSpeed) * Time.deltaTime
        );

        // Calculate pan from edge positioning:
        Vector3 mouseTranslate = new Vector3(
            (EdgeTranslate(Input.mousePosition.x, Screen.width) * mousePanSpeed) * Time.deltaTime,
            0,
            (EdgeTranslate(Input.mousePosition.y, Screen.height) * mousePanSpeed) * Time.deltaTime
        );

        transform.Translate(
            keyboardTranslate + mouseTranslate,
            Space.World
        );

        transform.position = new Vector3(
            Mathf.Clamp(transform.position.x, minX, maxX),
            Mathf.Clamp(transform.position.y, minY, maxY),
            Mathf.Clamp(transform.position.z, minZ, maxZ)
        );
    }
    
    float EdgeTranslate (float position, float boundary) {
        if (position > 0 && position <= edgeSize) {
            return -mousePanBaseSpeed * (edgeSize - position);
        } else if (position > (boundary - edgeSize) && position <= boundary) {
            return mousePanBaseSpeed * (edgeSize - (boundary - position));
        } else {
            return 0;
        }
    }
}