Flat design has came out and given the theory of simplicity is beauty.Flat design is totally different from those complex stuff or design,it depends on simple and light colours,vectors and simple typography.
The examples below describes why high end brands chosen Flat UI.
|This is Facebook Developer's logo|
Choose the colour wisely
I still love simple typography
Segoe UI in computer or you can use Open Sans for web-designing projects.They both have too much resemblance or even same.Both have light,semilight and lots of different font options to choose with.