Only if you look at the generated binary. But the source code which created this binary can be compiled to a myriad of other platforms with only minimal changes. You can compile the (mostly) same source code to JS+WebGL, iOS, Android, OSX, Linux (SteamOS), even Windows (but not Windows Store apps), ... The differences between these platforms is about 1% or 2% of lines of code in a typical 3D game. Compared to porting a game to, say the Xbox One or WiiU this is "peanuts".