This is one of the hardest challenges,and overall repetive if you *are forced to play it*.But noone's forcing you to play it though.Relax guys!(Challenge Difficulty:7/10)
I agree with Afro.Sure,we have to go to another website to play the game,but it's really the developer's choice to do whatever they want to their games.Heck,Sean can just not post the game here,and we would be in the dark not knowing that is a co-op Boxhead game.
The first power-up you should give to people is a "Transparancy" power-up.
The power is to make the bubble "Transparent",enabling the bubble to pass by other bubbles.A helpful power-up.
It's Greg's decision to make the next challenge though.Although there MIGHT be a chance this will be a challenge,if it has the API in it.
Not next yet though.
 "More Bloons"){kind=icon}
 "Boxhead: 2Play Rooms"){kind=icon}
 "Kongregate Racing"){kind=icon}
 "Multiple Categories Puzzle"){kind=icon}
 "Super Ixtipi Brothers"){kind=icon}
 "Smithys Quest"){kind=icon}
 "Torque"){kind=icon}
 "Heidi One"){kind=icon}
 "Luminara"){kind=icon}
 "The Endless Zombie Rampage"){kind=icon}
 "Bob's Escape"){kind=icon}
 "Float On (Beta)"){kind=icon}
 "Marvin Spectrum"){kind=icon}