I completely agree with what Vejtabul said, so here's my folow up idea: Place melee units onto the actual track, that can walk around a certain distance from where you placed them, and they can attack one bloon at a time, which will make that bloon stop. Maybe you could upgrade it to attack multiple units, or to gain a ranged attack, and maybe an ability to one-hit-kill everything that comes into range (except MOAB class bloons) for 10 seconds. + If you like...
To All: A little know fact is that balloons are actually lovely, they love to celebrate birthdays and stuff.... but bloons... *shudder*..... they are a public menace! And the monkeys are the only beings still alive that are capable of repelling these foul brutes!
An idea for a targeting option: Hit the most heavily populated area within range, so you could get area of effect towers to hit areas with many bloons, if you like press +
Guess what! The tower fountain information thingy says that the ace's ground zero ability doesnt harm MOAB class bloons, but it does! It destroys MOABs and BFBs!!! Honestly, this was the only reason i didn't ever get this upgrade, stupid tower guide thingy....
Such a good game, but now I am sad because I finished it :( Personally, i found that the archers with the elven upgrades were by far the best units in the game, followed closely by the ninjas and the chain lightning mages.
So, more days in a row makes it multiply the amount of monkey money you get, but i could swear that as this happens the amount of monkey money decreases.... today it got to 5x money, but it was only 13 monkey money...
*Day 91* The bloons' onslaught is never-ending. I fear that my many dartling monkeys will soon have to retreat into the monkey village, which is busy shooting lasers into our foes. This may be the end. ~ The Resistance
 "Color Pic-a-Pix Light Vol 2"){kind=icon}
 "Bubble Tanks Tower Defense 2"){kind=icon}
 "The Visitor: Massacre at Camp Happy"){kind=icon}
 "You are a... The Sequel"){kind=icon}
 "Interactive Buddy"){kind=icon}
 "Bloons TD 5"){kind=icon}
 "Dog Fight:The Ultimate War"){kind=icon}
 "Dogfight Aces"){kind=icon}
 "Wonderputt"){kind=icon}
 "Incursion"){kind=icon}
 "Enola: Prelude"){kind=icon}