How can I resize the game window to full screen and keep the same aspect ratio of the assets and UI controls?
To keep the aspect ratio in any monitor, you will have to resize the camera, it would be impossible otherwise I think 
So, for wider monitors, you’ll have to set a wider camera size. If the camera has multiple sizes, different players will se different scene areas, or you could use the classic black-borders 
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Thanks for help, but when i tried to change the camera, the On screen controls have been changed I think, or their hitbox has moved… I dont know for sure what happened.
Every layer has a main camera, maybe you didn’t resized the other layers cameras…