LookAt on only 1 axis for 2D games?

Questions & Answers
1

http://www.officegamespot.com/officegames/appleshooter.htm

Look at this game, the bow rotates based on where the mouse is

How can I make it? I’ve been trying for 5H (seriously!)
If you know quaternions/eulers please help me

Here’s my project (.unitypackage 0.5mb)
http://www17.zippyshare.com/v/85393294/file.html

I’ve came across this site: http://unity3dtutorial.com/unity-3d-tutorials/dealing-with-directions-movement-in-unity-3/
Maybe someone will find it useful, however I still can’t solve this problem

   	var mPoss = Camera.main.ScreenToWorldPoint(Vector3(Input.mousePosition.x, Input.mousePosition.y, 0));
	transform.position.x = mPoss.x;
	transform.position.y = mPoss.y;
	var r = (transform.position - center.transform.position).normalized;
	var t = Quaternion.LookRotation(r);
	transform.eulerAngles = Vector3(t.x,t.y,t.z);

Here’s another try

function Update () {
	var MouseWorldPosition = Camera.mainCamera.camera.ScreenToWorldPoint(Vector3(Input.mousePosition.x, Input.mousePosition.y, 1.0));
	MouseWorldPosition.z = 0;
	//find the target rotation quaternion
	lookRot = Quaternion.LookRotation((MouseWorldPosition - transform.position),Vector3.up);
	lookRot.y = 90;
	lookRot.z = 270;
	//rotate towards the mouse
	transform.rotation = lookRot;
}
/*	mPoss = Camera.main.ScreenToWorldPoint(Vector3(Input.mousePosition.x, Input.mousePosition.y, 0));
	obj.transform.position = Vector3(mPoss.x,mPoss.y,1.854246);
	lookDir = Quaternion.LookRotation(obj.transform.position,transform.position).eulerAngles;
	//lookDir.y = 90;
	//lookDir.z = 270;
	lookDir.x = transform.eulerAngles.x;
	transform.rotation = Quaternion.Slerp( transform.rotation, Quaternion.Euler(lookDir),Time.deltaTime*10);
//	lookDir = (obj.transform.position - transform.position);
//	lookRot = Quaternion.LookRotation(lookDir);
//	transform.eulerAngles = Vector3(lookRot.x,lookRot.y,lookRot.z);
//	transform.RotateAround(transform.position, Vector3.forward, lookRot.z);
//	transform.LookAt(Vector3(transform.position.x,obj.transform.position.y,obj.transform.position.z));
//	transform.eulerAngles.z = 270;
	//transform.eulerAngles.x += 90;
//	transform.eulerAngles.y = 90;*/
2

Here’s Code I wrote in order to get my cannon to rotate towards where my player clicks on the screen. It will only fire once it reaches its designated angle. Fully commented Hope it helps you out.

if (Input.GetMouseButtonDown(0))               //If the mouse was pressed.
            {
                centerTarget = new Vector2(0.0f, 7.3f);                                                                                                  //Sets center Target to always be straight up in the middle
                targetVector = new Vector2(mousePosition.x, mousePosition.y) - new Vector2(transform.position.x, transform.position.y);                  //Ses the target to be where the mouse is on the screen     
                newAngle = Mathf.Acos(Vector2.Dot(targetVector, centerTarget) / (targetVector.magnitude * centerTarget.magnitude)) * 180 / Mathf.PI;     //Sets the new angle value to be the angle between the center and the new target
                if (centerTarget.x < targetVector.x)                                                                                                     //If the new target is to the right of the center...
                    newAngle = -newAngle;                                                                                                                //make the angle negative
                targetAngle = Mathf.Round(newAngle);                                                                                                     //Rounds the new angle to the nearest unit.
                targetRotation.eulerAngles = new Vector3(0, 0, targetAngle);                                                                             //Sets the Target quaternion's euler to a vector with X and Y at 0 and Z at the new angle.
                targetObjLocation = Camera.main.ScreenToWorldPoint(new Vector3(e.mousePosition.x, Screen.height - e.mousePosition.y, 7));                //Sets the target objects location to be where the mouse is.
                isRotating = true;                                                                                                                       //Sets isRotating to true to tell the rest of the code its rotating
                Instantiate(targetObj, targetObjLocation, Quaternion.Euler(new Vector3(0, 0, 0)));                                                       //Instantiates the target object.
            }
            if (isRotating == true) //If the object is rotating
            {
                if (transform.rotation != targetRotation)          //If it hasn't rotated all the way to where its supposed to yet
                {
                    float step = rotatinSpeed * Time.deltaTime;                                                  //Set a step float to the rotating speed * Time.deltaTime
                    transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, step);     //Rotate gradually towards the new angle
                }
                else                                              //If it has rotated all the way to where its supposed to
                {
                    if(coolDown <= 0)
                        Fire();                                   //call the fire function
                    isRotating = false;                           //Tell the system its not rotating anymore
                }

            }