When you're in flow, it's hard to stop yourself and make sure all the css properties you are using have the right compliance.
Is there a way to analyze css files, and see where I could have used compass mixins to maximize browser compatibility?
SassMeister is a playground that specializes only in Sass-related stuff.
Of course, SassMeister lets you choose the syntax you feel more comfortable with and you even can choose the output style (expanded, compressed, and so on). Most importantly, because SassMeister is specific to Sass, it allows you to import Sass libraries (Compass extensions actually). You can even propose your own extensions if you think they should be added.