Pratham on Twitter: "STEP 4: The input fields are going to have a sunken effect. And to achieve this, we will use an inset box-shadow. As light is coming from the top-left
box-shadow | Codrops
CSS3 Box Shadow, only top/right/bottom/left and all · GitHub
A Quick Reference on Box-Shadows | Grio Blog
Box Shadow top, left and right - Axure RP 10 - Axure Forums