Apple Defender

Walkthrough:
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-Build three trees. 
-No weapons. 
-Wait for the worms to grab the first apple.
-Then build the first turrent by the exit.
-Build a second turrent when you can afford it.
-Upgrade both turrents to semi-machine guns.
-Build another apple tree.
-Build another machine gun.
-Repeat.
-When the “attack” worms come out, build repair towers.
-When you have enough cash to afford it, build a grow tower. 
-You first build a repair tower and then upgrade to grow. 
-When you have the money, upgrade to grow  2.
-Repeat.
-I also used slow towers for ovious effect. 
-By level 20, I had 5 machine guns by the exit, 3 machine 
 guns by the trees 1 grow tower maxed, and two slow towers. 
-The level 20 boss wiped 1/2 of my towers away but I was able to rebuild. 
-After level 20, the attack worms steadily were able to wipe away the 
 machine guns. I believe a machine gun/something else will be effective 
 after level 20 but I haven’t been able to find another weapon I have been
 impressed with. 
-The strategy will definately get you past level 20, but so far, I 
 haven’t been able to break level 30 yet.