It turns out that one game will actually be the next game in both the Bloons series and the Bloons Tower Defense series, at the same time. This enormous game will allow you to play in Bloons Mode (in which you just play Bloons 3), Bloons Tower Defense Mode (in which you just play Bloons Tower Defense 6), or Bloons Squared Mode (the mode the game is named after, in which you alternate between playing levels of Bloons 3 and rounds of Bloons Tower Defense 6). Each of these major modes also has sub-modes, of course.