X Factor

 is an Advanced Map in Bloons TD 6, released in Version 22.0 on December 3rd 2020 along with the Beginner Map Skates, and the Dartling Gunner.

Overview
Dirt terrain with loops. Bloons move diagonally along loops, alternating diagonal starting and ending each round in a very specific pattern. All bloons including MOAB-class are protected by the central tunnel system, although it doesn't block the line of sights otherwise. On every round, all bloons enter from two adjacent corners, come from either two lanes of each corner, and all exit to their respective opposite corner.

This also includes Undead Bloons that normally go through tunnel.

Starting from Round 1, the Bloons appear from the four paths in the top. On Round 2, Bloons appear from the four paths in the right, on Round 3 the Bloons appear from the four paths in the bottom and on Round 4 the Bloons appear from the four paths in the left. From Round 5 and later, the pattern of these 4 rounds repeats.

The large military stack in the middle can be removed for $2000. This will reveal more space for other towers, but it will not remove protection to the bloons travelling inside the tunnels. This military stack can fit at least one of any tower except a Banana Farm, which has the largest footprint out of all towers in the game.

Trivia

 * Despite this map showing 8 paths it actually has only 4 entrances and exits.
 * Its shown by use of "Pre-Game Prep" MK the map has 8 individual tracks causing 2 spike piles to appear instead of 1.
 * Because of this, it will almost completely tank Round 4.
 * This map is similar to the BTD5 map Z Factor in a way: the bloon track isn't direct, but consist of many small curves.
 * Because of the complexity of Bloon formations as well as the fact that the Bloons will be hidden in the middle of the map, this map is considered as one of the hardest Advanced Maps.
 * As this map came out with the dartling gunner, many aspects of the map can be attributed to boosting it, assuming you place the gunner at the middle. The top path benefits from straight pathways utilizing its pierce. The middle path benefits from the fact that there are no sudden turns in the track so it would not miss as much. The bottom path benefits from the ability to turn quickly and the fact that all pathways will end up getting close to it eventually.
 * According to a May 2021 graph, X Factor has the worst C.H.I.M.P.S. win rate of any BTD6 map other than Ravine (which had only just recently been made possible CHIMPS at the time), with its win rate being dwarfed by even those of every other Expert map.
 * X Factor is the first BTD6 map to have the letter X in it.