Still trying to get past the first level :p Love the real-time pathfinding though! Seems that there's a secret nav mesh that doesn't allow you to place block in some places. Very hard.
I reached lvl 5 :P It took me a while until I realized how to build a towers (not just a walls). Some bugs appears while building (it built the tower to adjacent cell instead). Anyway it is great, simple and addictive game. Good job :)
Loved the game. One suggestion: Add a sort of checkpoint option? After each level, show a code on the screen briefly that when entered will take you back to that level. Also, so this would work, have on the menu "Z" starts a new game and "X" brings you to the code input. The input could be done in a sort of padlock way with say 6 digits that you change with the arrows. When you are done, you press "Z" to finish. If the code is correct, it loads you to that level. If it is incorrect, it just says "Incorrect". You can press "X" again in that menu to just start a new game.
Played this game for at least half an hour though, love it!