Frustration

using UnityEngine;
using System.Collections;

public class MoveSquares : MonoBehaviour {

    public GameObject leftSquare;
    public GameObject rightSquare;

    public float speed;

    public float topPosition;
    public float bottomPosition;

    public bool leftGoingDown = true;
    public bool transitioning = false;
    public bool lifted = false;
    public bool firstMove = true;

    public bool coroutineRunning = false;

    void Start () {
        leftSquare = GameObject.Find("leftsquare");
        rightSquare = GameObject.Find("rightsquare");
    }

    void Update () {
        if (!coroutineRunning) {
            StartCoroutine(Movement());
        }
    }

    public IEnumerator Movement() {
        coroutineRunning = true;
        if (Input.GetButton("Vertical") && !transitioning) {
            if (firstMove) {
                if (Input.GetAxis("Vertical") > 0) {
                    leftGoingDown = false;
                }
                firstMove = false;
            }
            //flip direction
            if (Input.GetAxis("Vertical") > 0) {
                if (lifted && leftGoingDown) {
                    leftGoingDown = false;
                    lifted = false;
                }
            }
            else if (Input.GetAxis("Vertical") < 0) {
                if (lifted && !leftGoingDown) {
                    leftGoingDown = true;
                    lifted = false;
                }
            }
            //movement
            if (leftGoingDown) {
                leftSquare.transform.position += new Vector3(0, -1, 0) * speed * Time.deltaTime;
                rightSquare.transform.position += new Vector3(0, 1, 0) * speed * Time.deltaTime;
            }
            else if (!leftGoingDown) {
                leftSquare.transform.position += new Vector3(0, 1, 0) * speed * Time.deltaTime;
                rightSquare.transform.position += new Vector3(0, -1, 0) * speed * Time.deltaTime;
            }
            //transitions
            if (leftSquare.transform.position.y <= bottomPosition) {
                leftSquare.transform.position = new Vector3(leftSquare.transform.position.x,
                                                            bottomPosition,
                                                            leftSquare.transform.position.z);
                rightSquare.transform.position = new Vector3(rightSquare.transform.position.x,
                                                             topPosition,
                                                             rightSquare.transform.position.z);
                leftGoingDown = false;
                transitioning = true;
            }
            if (leftSquare.transform.position.y >= topPosition) {
                leftSquare.transform.position = new Vector3(leftSquare.transform.position.x,
                                                            topPosition,
                                                            leftSquare.transform.position.z);
                rightSquare.transform.position = new Vector3(rightSquare.transform.position.x,
                                                             bottomPosition,
                                                             rightSquare.transform.position.z);
                leftGoingDown = true;
                transitioning = true;
            }
        }
        if (Input.GetButtonUp("Vertical")) {
            lifted = true;
            transitioning = false;
            Debug.Log ("get button up");
        }
        if (Input.GetButton("Horizontal")) {
            //nothing happens
            //this is the joke
        }
        coroutineRunning = false;
        yield return null;
    }
}