Near the end of the movie, on the rooftop, Christine clearly states that there was always a safety net in place, so the game was never dangerous. As examples, she says that there was a diver ready if the main character couldn't escape from the taxi in time, and that the mysterious gunmen were only shooting them with blanks.

The gunmen fire these "blanks" during the scene at Christine's apartment, and the car chase directly after it. During the apartment scene, the gunmen shoot several holes in the wall and shatter various breakable objects in the building. During the car chase, they shoot and damage at least one car window. The last time I checked, you needed real bullets for these things. Some safety net.