A little harder than Forest Terrain, favoring Snipers instead of Ninjas, but still not much challenge on most tracks. Most tracks are single-laned or equivalent to it, with exception of Butterfly, which has two split lanes that exit and is the hardest of the Heavy Forest tracks. With exception of a lack of Farm to quickly snowball income, this terrain has no major setbacks in tower availability, except a small portion of Monkey Teams combos. The favored discount benefits Cripple MOAB in specific, making it viable as a ZOMG staller in the later rounds on the Flash version of Bloons Monkey City.
Specific to Butterfly, the straight lane at the start is the most strategic area to focus on. The best tower to use is Dartling Gun, since it can quickly switch between lanes at will, unlike Juggernaut, which, although good against the straight line itself, will suffer once Bloons (especially MOAB-class Bloons and their children) move past it.