Why my camera became a ball?

My camera became a ball instead of the default rectangle style, just after I created a new scene called mainmenu and created a canvas in that scene. This circle style camera makes my OnBecameInvisible() method become useless, and I don’t know how to fix it.

Can anybody tell me what is the reason that changes the camera style, and how can I change the camera back to the default rectangle style?

Thanks a lot for your help!

on top of the scene panel press on the gizmos text. it will turn on gizmos. and yeah it’s not a ball its a object rotation thing. W E R and T change object interaction menus