Most games use a "Layers" system rather than health bars. Popping a stronger Bloon reveals weaker "children" inside (e.g., a Blue Bloon contains a Red Bloon). Evolution of the Game Series
The franchise centers on a perpetual battle between highly intelligent monkeys and "Bloons"—sentient, balloon-like entities that vary in strength and ability. Related articles: "bloons"
The flagship series. Players place towers to stop Bloons from reaching the end of a path. BTD 1–6 , BTD Battles 1 & 2 , Bloons Monkey City Most games use a "Layers" system rather than health bars