Update comments

doc.go

@@ -77,7 +77,7 @@
 //
 // In the API document, 'the main thread' means the goroutine in init(), main() and their callees without 'go'
 // statement. It is assured that 'the main thread' runs on the OS main thread. There are some Ebiten functions that
-// must be called on the main thread under some conditions (typically, before ebiten.Run is called).
+// must be called on the main thread under some conditions (typically, before ebiten.RunGame is called).
 //
 // Environment variables
 //

run.go

@@ -31,6 +31,9 @@ type Game interface {
 	// Layout accepts a native outside size in device-independent pixels and returns the game's logical screen
 	// size.
 	//
+	// On desktops, the outside is a window or a monitor (fullscreen mode). On browsers, the outside is a body
+	// element. On mobiles, the outside is the phone's entire screen.
+	//
 	// The screen scale is automatically adjusted to fit the outside.
 	//
 	// Layout is called at an initialization and whenever the outside size is changed.