Ask HN: I have 9 months to build a strong portfolio. Any suggestion?

I have until the end of the year to build a portofolio to demonstrate my skills in the following frameworks/technologies/languages: AngularJS, ReactJS, RoR, Python, Go, Scala, Clojure, Android and iOS dev; and I seriously lack project ideas.

Do you have any suggestion?

I will take anything (web app, mobile app, programmer productivity tool, game, small interpreter/compiler, ...) provided it can be done in a small timespan (1-2 months), is challenging and will let me dig deeper in the technologies listed above.