0 - 1 Minutes Gone
– Use the Gatling Gun and upgrade the first two to level three.
– Start off by placing one of each near the vertical bridge, then move to the stepped corner just passed the same vertical bridge.
– Use them to block off the upper part of the map, forcing the runners to the south end. Make sure to then quickly block off the tiles to the right side of the map (forcing all runners over the vertical wooden bridge).
1 - 2 Minutes Gone
– Upgrade all middle and far left Gun Towers to level three to pick off any helicopters before they reach the exit (wasting very valuable time).
– Drop a Spark Tower just below the top entrance This’ll catch the top set of runners as they’ll slow down thanks to the new mini U-turn. Be sure to upgrade it to level three ASAP too.
2 - 3 Minutes Gone
– Drop a second Spark Tower down so it’s just above the southern entance’s horizontal bridge. This will help finish off any northern entrance runners and also damage the units at the south end.
– Swap out the turret opposite the top entrance with a Slow Tower (ideally the Polymorph one). This will maximize the damage dealt by the top Spark Tower.
3 - 4 Minutes Gone
– Always keep an eye out for a large number of runners coming out of an entrance, hit them ASAP with an item to rapidly take them all out, bringing in the next wave sooner (and it also allows you to buy new towers and/or upgrade quicker too).
– Swap out the Gatling Tower sitting above the northern entrance with a Flamethrower Tower and upgrade this to level two ASAP.
4 - 5 Minutes Gone
– Set down the radiation tower in the small square to the right of the southern horizontal bridge (see screenshot above).
– Use your Airstrike (or a Santa Strike) to take out slow moving units (such as Baby Tanks), otherwise you’re wasting loads of time that you simply can’t afford to waste on this level.
5 - 6 Minutes Gone
– For the final push, place down and upgrade a Tesla Tower and upgrade the Radiation Tower. Also, make sure all other Gun Towers are fully upgraded.
– If you’ve hammered the items out at the best times, you can be cleared with 20+ seconds still left on the clock. Using no items will make it really, really tough (harder than it needs to be really).