hide panels that a path hasn't been 'discovered' for yet

rather than showing the entire board, the reader/player must interact
with each panel to find a path. it's rather crude at the moment.
use image offset instead of adjusting everywhere

Kinetic lets you set an offset for images so the center of
rotation/animation/etc can remain unchanged. this also means any
calculations made throughout the code that was adjusting for this
doesn't need to be made because now image.x() and image.y() are at the
image center point.
add a little flare to revealing new panels