Bloons Tower Defense 5 - Daily Challenge 21 March 2013 (H.A.R.D)(NAPS)(N...

H.A.R.D - Beat Space Trunckin' on Hard with the "h", "a", and "d" hot-keyed towers. Three of each tower. Start at round 46. By KillerEX

Video is on 2x speed
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(Please comment if you have better strategy)
For more walkthrough: http://bloons-tower-defense-5.blogspot.com