The arm mechanic was an interesting concept, but it's execution was too sloppy was too frustrating to be considered anything but a failure. The controls may have been innovative and ambitious, but in practice they were an exercise in patience as you struggled to simply pick up a weapon only to have it knocked out of your hand by grazing a nearby object. It was given a 4.7/10 by IGN, a 3.9/10 by Gamespot and CVG gave it a 1/10, saying that "like John Hammond, they blew it.". Trespasser received a very harsh reception. All of this contributed towards a very immersive experience. It also featured HUD-free gameplay, your health was displayed on your breast and the remaining ammo on your clip was called out by Anne. Instead of just clicking on an item and picking it up, like a floating cam would, you had to extend your arm and grab it. At any time, you could look down and see your breasts/body. In addition to the realistic physics and ragdolls, it was also one of the first FPS games to put you in the body of a person, rather than just being a floating cam.
The ragdoll physics were remarkable as well, it was pretty awesome to kill a raptor and watch as it's body flops over and rolls down a hill. This may not be much now, but in 1998 it was mind blowing. Environment objects like baseball bats and hammers could be used to bludgeon dinos, with the amount of damage caused dependent on how hard the object was swung. Pushing one object into another would cause a reaction, and you could stack them and watch as they toppled over. You could reach areas by stacking boxes, or make a pass by tossing them out of the way. The player could lift an object, and drop it and watch as gravity took effect. Forget Half-Life, Trespasser did crate physics first.