– Use your initial cash to set a Gatling Tower on each of the tiles shown on the screenshot above.
– Initially focus on upgrading these towers before buying any new ones.
– Once you’ve got $90+, drop three Spark Towers in the middle of the map, in-line with the Gun Towers above and below.
– Before you focus on upgrading the Spark Towers, drop another two (one above and one below), so you’ve covered nearly the entire line from top to bottom.
– Once the Spark Towers are covering the full height of the map, spend some money on adding more Spark Towers closer to the towers nearer the exit as well as placing a few Ice/Slow Towers down beside the column of Spark Towers to maximise their effectiveness.
– Block off any remaining gaps in the Spark Towers (with more Spark Towers), so the only pathway for the ground runners are the three metal paths leading to the exit.