I feel there's a lesson to be learnt in this thread on asking a clear question.
So, here's what I assume you mean from 1-2 in Super Meat Boy
I'm guessing you're referring to the way that part of the background is lit up and part not, with those areas separated by by the circled line?
The area to be illuminated is found using just the kind of technique described in that tutorial I linked, with the polygonal outline of solid platforms being shadow casters. The lighting effect itself is an overlaid (subtly animated, in the case of Super Meat Boy) quad (either screen sized or with SMB's small levels, level sized). It probably uses the stencil buffer as set by rendering shadow shapes to determine where should be illuminated. The lighting quad is rendered using some kind of additive and/or multiplicative blend mode so that it brightens the background.
Interestingly if you press F11 while in-game it will toggle rendering of the lighting effect so you can easily see exactly what it's doing.
If that isn't what you're asking about, you're really going to have to be more clear.