I think it's a decent game, but there could definitely be some improvements to make it easier for the player to understand everything:
1) The biggest improvement would be to have a graphic to show the attack pattern/area of a unit type when the player is on the Recruit New Allies step. This becomes especially important when the fence keeps expanding because you want to be able to cover as much area as possible. Without this, players are simply picking whichever unit they want based solely on what it is and what the very *very* limited description says about it.
2) There should be a way to deselect a unit once a player clicks on its picture to build it. Currently once a picture is clicked on, it must be built. If the wrong one is accidentally chosen, or some new units come charging on right after it's picked and the player no longer wants that unit.....too bad
3) Some of the abilities of each unit type need an explanation with them. For example, my farmers early on gained the ability to grow apple trees. Ok.....what does that do for me? Do the trees act as a barricade on the field? Do they grant me some other bonus? So I planted one, and as expected it started producing apples. Once picking up the apple, I regained some health to build more units. Ohhhh, so the apple trees produce apples (obvious point), which in turn give you more buying power. A simple "Produces apples which restore hearts" sentence would have cleared it all up.
Other than that, pretty solid game. One other small improvement might be a speed up/slow down button during gameplay, similar to the one offered during the character chat times. This would alleviate some frustration from players who know their defense is solid and don't want to have to wait for the ensured victory.