Define GUI button

scene2d-ui is still so hardcore for my dumb brain. Anyway,
creating my own UI elements will probably let me tweak them
deeper later.
note to myself: always git pull before commit

Dear myself: if you pretend to work on the same project using multiple
comupters, please make sure you ALWAYS git pull BEFORE commiting
anything. Specially when you take long breaks between commit and
commit because you only work on your project on your spare time.

Now what? Double commit for the same file :\