Centered Path

"New central flight path for maximum map coverage."

- BTD6 description

 is the second upgrade of Path 3 for the Monkey Ace in BTD6. It adds a new targeting option "Centered Path" that sends the Monkey Ace along a circular path around a point (located at the center of the map by default). It doesn't matter where the Monkey Ace landing pad is for a Monkey Ace set to Centered Path; by default, they will all loop around the same path, albeit different parts of the loop depending on timing at which the player changes the loop setting.

Starting from Version 27.0, the center of the Centered Path loop can be manually changed per Monkey Ace. This allows it to be locked into a loop anywhere on screen at the player's own will.

It costs $255 on Easy, $300 on Medium, $325 on Hard, and $360 on Impoppable.

Summary
Centered Path adds an extra flight path that encourages free movement of Monkey Aces, letting them become less limited by placement of the Monkey Ace landing pads. Adequate timing of the Aces to align on the path smoothly might be necessary to optimize this upgrade, but purchasing this upgrade is very helpful on certain maps with good overall central circular track coverage.

Since Version 27.0, the option to choose the center of the loop now makes it possible to make a creative method of Ace micro based on Centered Path repositioning.

Tips

 * Besides just being an extra flight option, this upgrade is substantially useful on maps such as Park Path or Pat's Pond, although it is exceptionally more useful on the former due to how much more map coverage is utilized. On Park Path, 0-3-2 Bomber Aces can benefit a lot from this upgrade.
 * Monkey Ace upgrades that benefit the most from this target priority are the Upper Path 3 upgrades (Neva-Miss Targeting, Spectre, and Flying Fortress) and Sky Shredder. While utilizing just the plain middle Centered Path is helpful, a majority of the Centered Path's power comes from extreme micromanagement of the Centered Path centerpoints.
 * In the absence of utilizing extreme Centered Path micro, Upper Path 2 benefits little from this target priority, because the Centered Path upgrade misses out on purchasing Rapid Fire.

Trivia

 * This upgrade is one of many upgrades spelled in American English. What makes this fact interesting is that Ninja Kiwi is a New Zealand company, despite primarily using British English, especially when "-re" words are normally spelled as "-re" in New Zealand instead of the American "-er" (e.g. "meter" for "metre", or in this case, "center" for "centre").
 * According to the upgrade filename, this upgrade was originally titled Flight Orders. Revealed in an NK blog post, the upgrade was planned to allow the player to create their own flight path. It was changed for being "confusing, visually unappealing and honestly a bit overpowered."
 * The Version 27.0 buff to Centered Path has eventually lead to players in Version 28.3 to do multiple 2MPC completions with Ace with this upgrade. 3-0-2 Fighter Plane came first, followed by 0-3-2 Bomber Ace, and lastly 2-0-2 Ace.