You can use percentage if you want. I don't and don't know the things people do to adapt to different environments.
Having said that, every command you see in Tier 1 exists in Tier 2. So, whatever commands you use to do your percentage system in Tier 1 should work.
In order to make your Tier 2 app appear in full screen as a default, you need to change 'false' to true' in this call in the _tWinMain function in Core.cpp:
HWND hWnd = CreateWin32Window( hInstance, DEVICE_WIDTH, DEVICE_HEIGHT, szTitle, dwCenterWindowX, dwCenterWindowY, false );
This will cause the app to be full screen, but it won't have the header bar thing (with title, minimize, maximize, exit buttons) or any border.
And, it won't really know the actual resolution available on whatever Windows box it is running on. It will open full screen, but use the 'resolution' defined by the two DEVICE_<x> variables. It will expand everything to fit that size.
Even Tier 1 does not really know the resolution available in Windows. It uses the values in the setup.agc file.
On other platforms, like iOS and Android, it will try to get the actual resolution of the device. On the Mac, it works similar to on Windows, you set the resolution in the CoreForApp.h file.
Cheers,
Ancient Lady
AGK Community Tester