SOI's Singleplayer Adventure is a complete overhaul of the original Halo CE campaign, which provides updated graphics and new features. Every single aspect of the original campaign has been changed: characters, vehicles, weapons, even the BSP shaders and the musics. Other than aestethics, you will find also a wide range of weapons, each one with its unique functions. Assault Rifle has an attached grenade launcher (which acts like the Pro-Pipe from Reach), Rocket Launcher has an overcharged mode that fires faster rockets, Needler now is a burst-fire weapon, and so on. Vehicles have been improved as well, and same goes for the encounters and the actor_variants.