Bloonsday Device is designed with control decks in mind and is a counter to midrange or tempo decks. Bloonsday is the most expensive Bloon removal, and is the only removal that affects both players.
Although technically possible to use in Tempo, the nature of the deck wanting to attack the opponent means that Bloonsday Device may often get stuck in your hand and find very little use.
Since OTK decks don't really care about the Bloons they have on the board until they win the game, Bloonsday Device works well against opposing Tempo decks.
Bloonsday Device shuts down pushes designed to kill with one giant push, such as Golden Blimp + Double Trouble or any push that relies on slow, high powered Bloons such as The Regenerator.
Dreadbloon has a tendency to build up and string constant pushes of high delay Bloons, supported by its 80 card Deck, powerful removal, and Rock Bloons. Moreover, its playstyle disincentivizes playing offensive Bloons (except the Eternal, which is fine with Bloonsday Device). Because of this, using a Bloonsday Device will break Dreadbloon's momentum, allowing time to attack with Monkeys or recover from a board-wide Monkey removal. This is more useful for players who do not care about getting a high score.
Bloonsday is immensely expensive and can be very difficult to afford. Make sure to be wary of your own Gold alongside the opponent's Gold before using it.
As an Ultra Rare, it can be drawn by ULTRA Rare Power as a reliable way to obtain it. At max Gold, it's still too expensive to use both the same turn, making it not really a great strategy.
Bloonsday Device can be used to cancel a Red Bloon Apopalypse or to clear space for Storm Bloons. Using it this way should only be done in a pinch, as your opponent will likely capitalize off of the Gold you have spent.
During Version 6.2 playtesting, the nerfed Gold cost from 15 to 18 was decided due to its impact at limiting the choice to play other cards before affording the hard counter that would "destroy all Bloons", making it more predictable to anticipate and more risky to use early on.[1]
Gold cost increased ― 15 → 18![Teaser[2]](/images/thumb/3/32/BCS_bloonsday_device_teaser.png/83px-BCS_bloonsday_device_teaser.png)
Teaser[2]
Icon![Teaser[2]](/File:BCS_bloonsday_device_teaser.png)
