TODO

BUG LIST

WORLD 0 (intro)
    - black and white
    - first couple levels are just black char
    - maybe you have to backtrack?
WORLD 1 (meadow)
    - orange
WORLD 2 (catacombs)
    - yellow
WORLD 3 (dense forest)
    - green
WORLD 4 (ice cave)
    - sky blue
WORLD 5 (sunken tower)
    - deep blue
WORLD 6 (graveyard)
    - purple
WORLD 7 (forge/factory)
    - red

TO-DO LIST
    - zone editor
        + levels should be invalid if none of their exits are connected
    - buttons
        + create buttons (like in old cs50 demo)
        + toggle on/off buttons (maybe that move something)
        + toggle this/that buttons (switch between two states, maybe change color of pushable block)
    - keys and doors
    - changeable gravity

GAMEPLAY:
  - more objects: waterfall? decorative objects, like grass/insects/flowers/what else?
  - variable blocks - switches change them instantly from black to white. easy!
  - each of the level sets should have a gimmick:
      + water
      + ...and more!