Upstairs Downstairs

 is the 59th level in Bloons 2, and the 11th level in the Rubber Jungle zone.

Solution
Hit any Tack Bloon on the bottom in such a way that the dart hits each group of bloons towards the left. The Reverse Gravity Bloon there will always be popped regardless. For the next left group, the Ice Bloons should be hit with the dart bouncing off the Frozen Bloons and landing onto the top clump. AFterwards, the Reverse Gravity Bloon reverses gravity once again and should land a similar way as it did the last step and then bounce off the Frozen Bloons into the last clump of Tack Bloons.