Captain America himself is upgradeable, too. You'll need to upgrade these as you go, using game currency, which can be earned or purchased. As you progress you must recruit new S.H.I.E.L.D agents to help you tackle the increasingly mean opponents. The game has a strategic element to it, too. This includes the ability to throw your shield at enemies (which is a lot of fun I might add). Besides walking around bashing bad guys with your fists you can attack with a range of bombs and weapons.
Captain America: The Winter Soldier is a fun hack-and-slash romp, although it breaks little new ground.