You've been requesting it, and we're so excited to officially announce that co-op is coming to BTD 6! We don't have an exact date to share with you just yet as we're hard at work making this the best version of co-op that your awesomeness deserves, but here's a quick look at what you've got to look forward to! :D
https://www.youtube.com/watch?v=mD4WSJh9ZLc
Coming soon to Bloons TD 6!
Source: Steam Community (opens in a new tab)