Why my navigation bar dont hide?

[M1H4]

I have Lumia 535 with Windows 10 installed.When i open game, game opens on fullscreen,and when I hide a navigation bar below it stays black area.Here is screenshot prntscr.com/901gt5 .Does anyone know how to remove that black area? When i has installed Windows 8.1 navigation bar was as the Lumia 630

 

[rhapdog]

It's all part of the Insider program experience. I have several apps that exhibit the same issue, and some that behave properly. There are many apps where you cannot even hide the nav bar any longer. I've noticed it's almost exclusively games that have the particular issue you're having, at least in my personal experience with what I am using.

Just something we need to report and hope it gets fixed.