"Some of these changes were relatively trivial and did not make the game any less fun or compromise the vision of the designers. Others would require a lot of last-minute work and change the atmosphere of the game in significant ways. The team decided to keep the game as we originally submitted it to the ESRB, which meant shipping Halo with an M rating. This affects us significantly: M-rated games are not sold in certain national stores, not advertised in certain markets, and are often off-limits to young people. If any of these factors prevent you from getting your hands on Halo, we're sorry - we did what we felt we had to do."