Halo Zero is a fan made 2D tribute to the hugely popular Xbox series. Take control once again of Master Chief and battle against the Covenant invaders.
If the generic sci-fi story of the original Halo games was obscured by their ambition and scale compared to older shooters, it certainly isn't in a 2D 16-bit era landscape. You control the suited space marine, and shoot your way through a variety of forgettable alien onslaughts.
The graphics, as mentioned, are very 1990s, and although they have clearly been created with some care they seem uninspired. Control is via the keyboard and mouse, aiming and firing with the mouse, and movement and other things with the keyboard. It's quite a good system, and you can configure the keys as you like, which is useful.
Gameplay itself is a mixed bag. The sound effects are excellent, with great weapon effects, but the combat is untidy - you can't always see alien gunfire which makes avoiding it awkward!
Halo may have been a landmark 3D game, but Halo Zero does not make the same impact in the world of 2D platform shooters. It's probably one for hardcore Halo fans only.