Circle Blue (ScrapTD)

Circle Blue is the first barrel in ScrapTD and is automatically unlocked.

Strategical use
When the game came out, Circle Blue was a true killer. But it has been nerfed a lot and is practically useless right now in terms of doing damage, it's not a problem if some get to the base, because even on level 20 it does less damage than Square Pink or many other barrels do at level 1. The only sense in upgrading it is for getting xp.

In the lower arenas it is actually a bit stronger, because there are some which don't defend, but it can be defeated easily.

It's mostly used to get some scrap.

Surprisingly, Circle Blue on levels 11 and higher can change interactions with Square Blue on level 1-9, meaning the enemy's underleveled Square Blues will struggle to it and requires at least 3 to defend it, but it's not really a common strategy since it does require 3 hits to be destroyed, but isn't really necessary but can be a bit strong in the lower arenas.

Overall use
Circle Blue albeit is necessary to send during the early game. Sending them is the way-to-go plan to increase your scrap production by 12% of it's cost so you can build up your income faster early on and then send Square Pink if you have enough scrap to do so.

It's not necessarily the barrel which does damage though, so it can get defeated by 2 Square Blues and that's pretty much it.

Trivia

 * It was one of the first two barrels in the game, in the alpha, together with Square Pink.
 * Circle Blue, Coal, Mobile Delivery, Not Too Fresh and Chrome are the only barrels which don't deal 50 damage at level 1.