Everything is working, with some bugs:
a) occasionally it misreads distances and bugs out
b) occasionally moves at 225 degrees instead of 45 to reach the grid
intersection
c) x & y position displayed are in their hundreds, though the bot makes
it to 0,0 with no problems
d) light sensor sometimes reads the second line too early (immediately
after first)
e) if bot starts too close to grid cross it moves to the next grid cross
(doesn't read the first line)