Bloons Tower Defense 6 (BTD6) is a tower defense game, where the player place monkey towers to pop and destroy balloons trying to reach the end of the map. The game allows Singleplayer and Cooperative Multiplayer on both PC and Mobile platforms. It was initially developed as a tower defense flash game on the browser and the series was launched which included the development of other similar games with the theme of balloon popping (Bloons Monkey City, Bloons Tower Defense Battle etc).
The gameplay like, other tower defense games, is simple to understand and pick up. The player has money which can be used to buy different types of towers with different effects and use them to attack(pop) the balloons trying to reach the end of the map which will cause the player to lose lives. Towers have different attacking types, some having an area of effect attack while others specialise in popping multiple layers, slowing the balloons down, or providing utility effects like buffs to other towers. The towers can be upgraded into different paths to specialise in different effects, allowing many combinations and strategies. The balloons, unlike other tower defense games, have health in the form of layers. For example, red balloons take one pop to be destroyed, blue balloons take one pop and release red balloons. Balloons increase in layers with each layer releasing lower tier balloons when popped. Some types of balloons also have special abilites such as being stealth from most towers (camo) or requiring special popping power (lead). There are also giant balloons that release many stronger balloons and require a lot more attacks to be destroyed.
This requires the player to strategise how to combine different kinds of towers and lay them out optimally in order to be able to handle the different kinds of waves the game sends (Lens of Problem Solving).
All the maps also have difficulty levels which changes factors such as lives and costs of towers and upgrades to challenge the player (Lens of Challenge). This ensures that difficulties can be suited to each player’s preference and players do not find the game too easy after playing for long.
The game features different kinds of maps with varying difficulties for the player to play on. Each map is unique in the pathing of the balloons and the areas that the player can build on. Some maps also have hidden secrets like pressing a button for redirecting balloons or mechanics like requiring money to unlock more areas to build towers on (Lens of Secrets).
This makes each play of the game different and interesting as the strategy for tower placing is always new.
At the start players are given only basic towers to use and these towers do not have any upgrades unlocked for purchasing yet. Players have to use the towers in order to gain experience and these experience points can be used to permanently unlock the different upgrade paths to allow players to purchase the upgrade in the game. There is also a rank system for the player that unlocks more towers on rank up and also grants players skill points to be used for spending on skill trees that give permanent buffs to towers and gameplay. On completion of maps, players are awarded badges that is shown on their profile page.
Players can spend skill points depending on what towers they want to focus on in the game, for example utility towers or specialised towers (Lens of Meaningful Choices).
When playing cooperative multiplayer, depending on the skill trees of the players, different players can choose different roles depending on the towers they build (Lens of Cooperation).
The experience, rank, skill tree system and badges are not only essential to the gameplay but also shows the progress and time spent by each player to achieve the rank which differentiates casual players and hardcore players (Lens of Visible Progress).
This game focuses largely on game mechanics, having many towers with different kinds of projectiles and balloons with special properties. The storyline is short and simple, monkey popping balloons. Towers have interesting identities such as the Super Monkey which is a powerful tower imitating a super hero or Banana farms which is used for currency gain with the idea of ‘farming money’. With this weird storyline as a theme, the game uses cartoon graphics and animations to design each tower and balloon (Aesthetics). As this game was initially developed as a flash game, it retains the technology required which is simple keyboard and mouse inputs. Since BTD5, it has also been developed on mobile platforms to allow people to play on the go. From BTD1 up till BTD6, every release brings new types of monkeys and upgrade changes which is shows the development of the game mechanics that the game focuses heavily on.