I found that the best way to make this game work is to build a tube around the path the attackers take.
Since their logic forces them not to think ahead, they are easily killed before its too late. Later in the game, its how slow you can get them while killing them off that is the trick, so adding an alternate slowing element, with rocket towers works fine.
Don’t bother with anything other than rocket towers for destruction. Don’t bother raising the heights of towers for more range, its a waste and slows the response of the towers.
Build starting from your cookie fortress and work your way out, toward the path of advancing attackers. Below is a view of what works well for me, and has resulted in all cookies saved on the hard level right to the end. Once its built, you can sit back, relax and let it play out.
The Symbols Are
C = Cookie Fortress
G = Green Grease Tower
R = Rocket Tower
O = Oil Tower
P = Paint Tower
W = Water Tower
Here is What it Looks Like When I’m Done
R
P
R R
W G
R R
O
R CCCC
CCCC
CCCC
CCCC
It’s Not a Bad Idea to Have a Plan so Here is the Step-by-Step Walkthough I Use to Make This
First a tower one space away from the corner, upgrade to rocket with the starting pieces.
R CCCC
CCCC
CCCC
CCCC
The next tower can’t be built until you have enough pieces. I recommend making it a cannon tower quickly, then upgrade it to rocket.
R
R CCCC
CCCC
CCCC
CCCC
Now build outward, each time exactly one up, and one more left from the previous, in the next layer add two towers. First make them each a bag tower, then upgrade each one, one by one to oil, and green grease. It doesn’t matter too much which tower first or grease or oil first, but its a powerful combination.
G
R
O
R CCCC
CCCC
CCCC
CCCC
Add a layer of rocket towers. I recommend first adding one tower, upgrading it to rocket, then add the second one and upgrade it to rocket.
R
G
R R
O
R CCCC
CCCC
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CCCC
Now the next layer of slowing towers. Again, start with two bags, then upgrade. Upgrade one to Green grease or oil, but I find it easiest to leave them both as oil since the plan is further upgrading later.
O
R
O G
R R
O
R CCCC
CCCC
CCCC
CCCC
Upgrade the Two Outer Oil Towers to Water and Paint
P
R
W G
R R
O
R CCCC
CCCC
CCCC
CCCC
Add a Final Outer Layer of Rocket Towers
R
P
R R
W G
R R
O
R CCCC
CCCC
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CCCC
By wave 17 (with the fast guys), you will want to add an extra pair of inner rocket towers, as sometimes one or two attackers will barely make it though without them. You could skip this, and get to level 20, but you will lose cookies if you do.
R
P
R R
W GR
R R
O
RR CCCC
CCCC
CCCC
CCCC
Its done, if you built this, it will stand up to level 17-20 right to the end. I usually never lose a cookie with this design. – Bret Zenther