[T-Rex]

The first one was pretty much like office buildings and stuff.

The second one opened it up to jungle camps and city streets.

The third one stuck more to the city streets and building levels.

The fourth one introduced arctic landscapes, city streets, a cruise ship and a hotel.

In the fourth, Sam's a Double Agent pretending to be a Terrorist. It still uses the "hide in the dark" style of play, but it's not as heavily dependant on it as seen in the previous games. It's more of a "hide under a table or behind some crates" type thing. Basically, a Splinter Cell Metal Gear without a Metal Gear. Not as fun as 2 or 3 in my opinion, just way better looking.