How do I a streetfighter style camera?

I need a camera that follows the characters, and that the characters collide with the edges in the style of Street Fighter or Mortal Kombat.

I already have a project base, I have some characters and their movement, but I need to know how to make a camera of this style.

It's something like this: scirra.com/arcade/fighting-games/rec-jp-fight-12708

I do not need you to send me a finished game, I just need to know how to make that kind of camera, thanks.