Unlike the traditional FPS view of his earlier games, Manhattan Project is a 3D platform-shooter (often called a "2.5D" game). You view Duke from a third-person, isometric-like angle as he runs, jumps, and blasts his way through the streets of New York.
Duke Nukem: Manhattan Project is a side-scrolling video game for the PC is now only available through ZOOM Platform. Duke Nukem Wiki