The Bloonsday Device is a Special Agent in Bloons TD 5 that was released on March 1, 2012. It is the most expensive Special Agent, currently costing 250 (previously 500). The Bloonsday Device will send out beams that will follow wherever your cursor is, and these beams can and will destroy most Bloons easily. This ability is very powerful and can only be used for a short time (the beam lasts 12 seconds on normal speed and 5 seconds on fast forward speed). It also goes through a cooldown before reactivating.
Because the power of this attack pops Bloons almost immediately, it's better to use the beam on normal speed because you have more time to move your cursor.
When the round ends, the beam continues, so start the next round quickly and place the beam at the start.