The design of the Forerunner weaponry in Halo 4 has provoked some contriversity, with many people saying that the design does not match previous Forerunner weapon designs.
The builder Clan, which built the Halo Array, were master architects. Their designs were smooth and flowing, and tried to mimic natural structures. They built the Halo rings, and everything on them, including the senitals and moniters. The sleek, silver lines of Builder design can be seen on all these constructs, as well as the weapons, such as the senital beam and auto-turret.
The keyship, and the sentinels have Forerunner design, like all things on tha Halos.
The weapons and enviornments in Halo 4 are on a shield world, and have warrier-servent design. They are designed to look indidminating, with hard lines, and oringe and red lights.