Had it all right but missing to much.
Each weapon has its own special "Reality" side to it, some guns require you to place into a bump position and repeatedly press a button to pump it up or charge it. Your flashlight and NightVision work on a pump as well that must be checked every so often to repump. The areas of the maps that require you to wear air masks that are timed by your own watch, must be replaced by pushing a button before the timer runs out(or gagging starts), and your mask can even break and if any fractures are made you start to gage to death.
The graphics are also amazing. The story is great - makes sense. A lot of areas let you choose whether to go all out crazy and kill everyone or go in stealthy. They give you many opportunities in the game even with such linear game play to choose what to do or where to go in the area.
Its hard for me to understand why some reviewers on this game bash it for its game play, when it seems they've barely played it. The weapons alone add something that no game has ever gone down. The areas and monsters in the game are unique and quite scary. Metro added a lot of fun and different elements but left out a lot of other elements that could of made it a heck of a lot better, but it evens its self out.
If Metro and Stalker got together and made a baby. Oh boy we are looking at one of the craziest Best Game of the Year Awards hands down! But sadly this is the 20th century so game companies aren't thinking of everything they can add to their games to make it good, just what works.