I can say I've known css to an extent like creating layouts, styling ur page, creating inline/external stylesheets, writing mediaqueries, formating web pages. What else do i need to know in css b4 I proceed to the next level.

Gain mastery over it, create gravity-defying layouts. Take the box model and think outside the box.

As to what else CSS is used for....well the answer lies within you. Let your creativity answer that.

Make sure you are creative enough on it before moving to the next level. Create menus also.

u can also use it to create android apps

If you have already learned and mastered OOCSS and Responsive Web Design, I would say there is not much else there is to learn, as far as CSS is concerned. At this point, you can choose to either read up on specs for later releases or just like with the Bible (assuming you are a christian), read over what you think you know again so as to be "spritually" fortified against "the evil one"

Good luck!

Thanks.

Have you learned how to style what is called 'mega drop down menu'?
A kind of drop down menu that has up to 5 columns with images in the columns.
Have you mastered Responsive design or fluid design?
Have you gotten a grip on positioning, z-index and stuff like which confuse lots of css students.?