Wave 01
Build Wee Ninja huts on squares 1 and 2, and an Anti-Ninja hut on square 3. Fast-forward to start the demons. At the end of the wave build a Sniper Ninja hut on square 4.

Wave 02
At the end of the wave build a sniper on square 5.

Wave 03 to 06
You shouldn't need to do anything, just be ready to give your Ninjas a tap if they need to catch a runaway.

Wave 07
At the end of the wave upgrade your Anti-Ninja hut on square 3 and build an Anti-Ninja hut on square 6. If you have time before the next wave begins, upgrade both your sniper huts.

Wave 08
If you didn't manage to upgrade your snipers at the end of wave 7, do it at the end of this wave.

Wave 09
Upgrade your Anti-Ninja hut on square 6.

Wave 10
You should be fine on this wave, but be ready with your special powers just in case.

Wave 11
At the end of the wave, upgrade both your Anti-Ninja huts.

Wave 12
Again, you should be ok but be ready with your specials just in case.

Wave 13
At the end of the wave upgrade both of your snipers.

Wave 14 to 15
Your defences should hold, but get ready with your wind on the off-chance that a demon slips through. You will also have a ton of cookies at this point, so feel free to upgrade your huts at the end of the waves if you need the reassurance.