text: Though the maps are nearly identical to their appearance in Left 4 Dead , No Mercy in Left 4 Dead 2 contains all of the enhancements of the sequel , including the new Special Infected , Uncommon Infected , melee weapons , additional guns , and the ability to use the new game modes , including Mutations and Scavenge mode .
simplified: Left 4 Dead 2 brings new elements to the game that Let 4 Dead left out in the previous version such as melee weapons , new types of infected , and a story-arc that connects each of the game 's five campaigns together .