This is a video of me, Tasselfoot, beating Track 1 of BTD5 Bloons Tower Defense 5 on Hard Mode without losing a life. I use one of the secret agents to make things easier... you can easily follow this strat and replace the secret agent with a few road spikes on the appropriate levels.

Video is on 3x speed.

Game: http://ninjakiwi.com/Games/Tower-Defense/Play/Bloons-Tower-Defense-5.html