NEW MIRAGE SOURCE

[Pbcrazy]

You'd be better off remaking it in Java and OpenGL, that way you can get the most cross-platform-ability (lol) out of it, plus then you get browser support, and it'll run 5x better than with Unity (which is primarily a 3D engine, and a very slow one at that).

If you plan on mobile and mac/linux gaming, you'll have to use OpenGL, as DirectX is a primarily Windows library.