Bloons TD Battles Mobile

"Play the top-rated tower defense franchise in this all new head-to-head strategy game - FREE! It's monkey vs monkey for the first time ever - go head to head with other players in a bloon-popping battle for victory. From the creators of the best selling Bloons TD 5, this all new Battles game is specifically designed for multiplayer combat, featuring 14 custom head-to-head tracks, incredible towers and upgrades, all-new attack and defense boosts, and the ability to control bloons directly and send them charging past your opponents defenses."

- Ninja Kiwi description on Google Play

 (known as BTDB for short) is the mobile version of Bloons TD Battles and was released on July 18th 2013. This version, unlike Bloons TD5 Mobile, is free to download on the App Store and Google Play.

Features
Bloons TD Battles Mobile introduced features that were not included in Bloons TD Battles.
 * Private matches are set up by Facebook invite for Android. Facebook and Game Center invites can be sent for private matches on iOS. Players can choose a track.
 * When the player unlocks a tower, only the tier 1 and tier 2 upgrades are unlocked. Tier 3 and 4 upgrades need to be unlocked separately with Medallions once a certain Battle Score has been reached.
 * There is a tutorial that is CPU-controlled at the beginning of the game. The tutorial can be replayed at any time by choosing Play.
 * There was a bug which made it impossible to finish the tutorial. It occurs when the player must buy a bloon but has just spent his/her money, and can't get any money and has have to surrender. This has been fixed (the game will give money to the player).
 * There are tracks exclusive to the mobile version.
 * The Heli-Pilot, Bloonchipper, COBRA and Monkey Engineer can be unlocked.
 * Playing games does not require any Battle Energy. As such, there is no limit to how often a player battles. Battle Energy is instead used as a special currency to purchase boosts and other items.
 * The player only has access to three towers slots per game; however, their final tower slot can be unlocked temporarily for 1, albeit being randomised. If the player is dissatisfied with their final random tower, they can randomize again at a cost of an additional 3.
 * Players can also "skip" a track for 2, changing said track to another random track. This can be used two times per game.
 * Players can purchase a Tower Boost or Bloon Boost for 1 in-game, speeding up the attack rate of Towers or the speed of sent Bloons, respectively, for a short time, both of which have a cooldown time.
 * Players can also purchase a stack of White Hot Spikes for 1 in-game, unlike normal roadspikes, they don't disappear after the round has ended, they pop 20 bloons and can pop lead bloons.
 * There is a practice mode in which the player can play alone in Defensive mode and go as far as they can - similarly to the core gameplay of the Bloons TD games.
 * As of August 18, 2014, there now is a tower exclusive to Bloons TD Battles Mobile called the COBRA. This tower will not be released on other platforms because of how it has been customized exclusively for Bloons TD Battles, with upgrades affecting the Bloons sent out and lives gained.
 * There are club rooms that have special rules such as unlocking Bloons to send earlier, getting double cash, and getting a free random tower.

Most recent update
Version 4.3. Includes bug fixes and balancing changes. In general, certain towers and certain upgrades have decreased price and more of other benefits.

Trivia

 * The White Hot Spikes is similar to the Red Hot Spikes in Bloons Monkey City, as they both have properties of not disappearing until all 20 spikes are used up.