No obvious ability to turn off the sound. And no objective besides just lasting as long as possible. Esc nor the p button paused the game. just some simple things that I saw.
The bomb that floats around doesn't give you credit for any of the bloons popped by it. Using it to wipe out a large group of bloon could keep you getting a gold rank.
 "Pearl Harbor 1941 V2"){kind=icon}
 "Dragon Ambush 2"){kind=icon}
 "Bloons Super Monkey"){kind=icon}