The type or namespace name 'OS' does not exist in the namespace 'osu.Android' (are you missing an assembly reference?)

The type or namespace name 'OS' does not exist in the namespace 'osu.Android' (are you missing an assembly reference?)

'Environment' is an ambiguous reference between 'Android.OS.Environment' and 'System.Environment'

'OS.Handler?' does not contain a definition for 'Post' and no accessible extension method 'Post' accepting a first argument of type 'OS.Handler?' could be found (are you missing a using directive or an assembly reference?)

'OS.Handler?' does not contain a definition for 'PostDelayed' and no accessible extension method 'PostDelayed' accepting a first argument of type 'OS.Handler?' could be found (are you missing a using directive or an assembly reference?)

'Environment' is an ambiguous reference between 'Android.OS.Environment' and 'System.Environment'

'Environment' is an ambiguous reference between 'Android.OS.Environment' and 'System.Environment'

The type or namespace name 'OS' does not exist in the namespace 'osu.Android' (are you missing an assembly reference?)

The type or namespace name 'OS' does not exist in the namespace 'osu.Android' (are you missing an assembly reference?)

The type or namespace name 'OS' does not exist in the namespace 'osu.Android' (are you missing an assembly reference?)