I loved this game, then thought it was just based on a bunch of luck at harder levels, but kept playing because the concept was wonderful. Now that I've beaten it a few times on "Harder" mode, I am starting to see strategies that work to help overcome more difficult initial surrounding squares, and I'm back to loving it again.
Now, what changed from v1.19 to v1.21??
 "Rebuild"){kind=icon}
 "Target Practice"){kind=icon}