Towers
=====

Build a tower on every square so that each row and
column contains every height of towers only once and
that the clues on the edges match.  The clues 
describe the number of towers visible when looking
from that edge, taking into account that bigger 
towers would obscure smaller ones.

Use L and R to choose a number.
A-click on a square and press X to enter the number.
B-click on a square and press X to enter some provisional
numbers in that square.
