XY Movement Code

// Minimum and Maximum Ranges
private float minX;
private float maxX;
private float minY;
private float maxY;

// Start Method, Game Space
float distance = transform.position.z - Camera.main.transform.position.z;
Vector3 leftMost = Camera.main.ViewportToWorldPoint(new Vector3(0,0,distance));
Vector3 rightMost = Camera.main.ViewportToWorldPoint(new Vector3(1,0,distance));
Vector3 bottomMost = Camera.main.ViewportToWorldPoint(new Vector3(0,0f,distance));
Vector3 topMost = Camera.main.ViewportToWorldPoint(new Vector3(0,1f,distance));

minX = leftMost.x + padding;
maxX = rightMost.x - padding;
minY = bottomMost.y + padding;
maxY = topMost.y - padding;

// Update Method, Horiztonal, Vertical and Diagonal Movement
        if (Input.GetKey (KeyCode.UpArrow)) {
            if (Input.GetKey (KeyCode.LeftArrow)) {
                transform.position += Vector3.up * speed * Time.deltaTime;
                transform.position += Vector3.left * speed * Time.deltaTime;
            }
            else if (Input.GetKey (KeyCode.RightArrow)) {
                transform.position += Vector3.up * speed * Time.deltaTime;
                transform.position += Vector3.right * speed * Time.deltaTime;
            }
            else {
                transform.position += Vector3.up * speed * Time.deltaTime;
            }
        }
        else if (Input.GetKey (KeyCode.DownArrow)) {
            if (Input.GetKey (KeyCode.LeftArrow)) {
                transform.position += Vector3.down * speed * Time.deltaTime;
                transform.position += Vector3.left * speed * Time.deltaTime;
            }
            else if (Input.GetKey (KeyCode.RightArrow)) {
                transform.position += Vector3.down * speed * Time.deltaTime;
                transform.position += Vector3.right * speed * Time.deltaTime;
            }
            else {
                transform.position += Vector3.down * speed * Time.deltaTime;
            }
        }
        else if (Input.GetKey (KeyCode.LeftArrow)) {
            if (Input.GetKey (KeyCode.UpArrow)) {
                transform.position += Vector3.left * speed * Time.deltaTime;
                transform.position += Vector3.up * speed * Time.deltaTime;
            }
            else if (Input.GetKey (KeyCode.DownArrow)) {
                transform.position += Vector3.down * speed * Time.deltaTime;
                transform.position += Vector3.left * speed * Time.deltaTime;
            }
            else {
                transform.position += Vector3.left * speed * Time.deltaTime;
            }
        }
        else if (Input.GetKey (KeyCode.RightArrow)) {
            if (Input.GetKey (KeyCode.UpArrow)) {
                transform.position += Vector3.right * speed * Time.deltaTime;
                transform.position += Vector3.up * speed * Time.deltaTime;
            }
            else if (Input.GetKey (KeyCode.DownArrow)) {
                transform.position += Vector3.right * speed * Time.deltaTime;
                transform.position += Vector3.down * speed * Time.deltaTime;
            }
            else {
                transform.position += Vector3.right * speed * Time.deltaTime;
            }
        }

        // Restrict player movement to game space
        float newX = Mathf.Clamp (transform.position.x, minX, maxX);
        float newY = Mathf.Clamp (transform.position.y, minY, maxY);
        transform.position = new Vector3(newX, transform.position.y, transform.position.z);
        transform.position = new Vector3(transform.position.x, newY, transform.position.z);