Download from here :- http://is.gd/nj1ZOd
You’ll notice an arrow path showing where your enemy will run, positioning your players on the grid can alter the direction in which they run, however, you cannot completely block their path.
My personal technique in tower defense games is to make sure to crowd their launch point with heavy artillery and take out as may on the start as possible.
Yet Goal Defense is brilliant and even more challenging as you cannot just place all your eggs in one basket with that strategy as the launch point can change mid game, or a bus load can be transported into a different launch point.
Therefore you must have enough cash to position defenders where needed.