Things pick up a notch from the last map as several new units are brought into the mix (such as the Mamma Tank). The key is in making use of the two looping sections in the centre.
Waves 1 - 10
– The key to beating this on Heroic is to dominate the left-hand side of the map early on so you never need to worry about them reaching the exit.
– Drop a couple of Gun Towers at the top of the first loop (one on each upper corner) and upgrade both of them ASAP.
– Add a third on the middle partition (so it’s sitting level with the other two) and upgrade this fully as well.
– By round eight you’ll want a fourth tower located on the bottom-left corner of the loop, this will deal additional damage to some troops as they show up, but it’s more for taking down the helicopters that show up in round nine.
– On round 10 a couple of Mamma Tanks will make an appearance for the first time, if you have any items on standby, now’s a great time to wait for them to bunch up together by the loop and hit them with an item for a quick and easy combo kill.
Waves 11 - 20
– With the money from the last wave, use it to buy a Hive Tower and place it directly below the top-left most gun tower. The radius on the Hive Tower will not only cover the trench entrance, but also pick off any air-based units that try and sneak past below you.
– Upgrade the Hive Tower once and then drop a slow tower in between the Hive and the Gun tower below. This provides a very formidable defence that will slow down approaching units, allowing the Hive Tower to deal serious damage before they even reach the trench entrance.
– Drop another Gun Tower on the middle partition, this time at the bottom, this’ll finish off against any choppers that make it past your first line of towers. Now focus on upgrading your remaining towers.
Waves 21 - 30
– Your key focus now is to earn enough for a second Hive Tower and drop it on the grass located in the top-left corner of the map. Placing it on the corner by the entrance to the trench will substantially increase the damage two Hive Towers together can cause.
– Now focus on saving enough cash for a Flamethrower (which you should have unlocked by now if you’ve been following our guide), otherwise buy a Missile Tower and place it in the centre of the loop.
Waves 31 - 40
– Place a Slow Tower on the middle partition (just under the bridge) as this will catch any units as they come into the loop (and will also allow you to catch anyone that happens to make it to the metal bridge itself). Don’t forget to upgrade it to level three ASAP.
– Spend the next few waves upgrading all remaining towers to the highest level and then once that’s done, plug the final gap between the top two towers with a Missile Tower for some decent additional damage.
Waves 41 - 50
– You should have built up a decent cash reserve by now, so place a Hive Tower to the left of the bottom leftmost Gun Tower as its 3.5 grid radius will allow it to start damaging units as they appear on the map.
– On the final wave, S-17’s will show up with some Momma Tanks. There’s a high chance with this tower setup you’ll slow it down so much, that it’ll explode right over the tanks below, speeding things up nicely.
– Odds are you’ll also have an unused Airstrike. Might as well call that in to finish off the last S-17 as it enters the map (assuming you’re not then going to play Endless mode, otherwise save it).