Search a specific mac os x tool - Semi transparent layer over entire screen

Hey there,

I´m searching a specific tool, that I´ve seen a couple of days ago at university.

The tool makes it possible to slide a semi-transparent layer over the entire screen to show some cheat sheets with keyboard shortcuts for different apps.

Does anybody know what it ist?

Thanks for answering!

 

no its something other. the transparent layer slides slow in from the bottom edge of the screen when you hit the key