Blocks have to be in the air. Once they've touched another block or the ground, they don't count as in the air. If you check the stats page you can see how many in air clicks you have. Achievements page is visually bugged. Its been fixed for the next update. Thanks for the bug report.
Yeah a room with 2 doors in front of them just to get in another empty room.. Why did you make keys ? the only thing your get with these are empty rooms or rooms full of zombie (Oh yeah gread thats a nice Bonus finding a key open a door and then it's full of hungry zombies what a happy moment)
Solution for level 9: Create 4 SAM Towers and replace them if they where destroyed, thats all, then wait until you have enough money and start your attack
 "Incremancer"){kind=icon}
 "NGU INDUSTRIES TESTING"){kind=icon}
 "Idle Stacker Kongregate Edition"){kind=icon}
 "Arkandian Crusade"){kind=icon}
 "Build & Destroy Space (update)"){kind=icon}
 "Arkandian Explorer"){kind=icon}
 "Trollface Quest"){kind=icon}
 "Insidia"){kind=icon}
 "CellCraft"){kind=icon}
 "The Devil's Angel"){kind=icon}
 "Epic War 3"){kind=icon}
 "Deadly Waters"){kind=icon}
 "Happy Pleated Skirt Cutie"){kind=icon}
 "MagicPen2"){kind=icon}
 "Zombie Infestation: Strain 116"){kind=icon}
 "Sky Invasion"){kind=icon}
 "Get Off My Planet"){kind=icon}
Blocks have to be in the air. Once they've touched another block or the ground, they don't count as in the air. If you check the stats page you can see how many in air clicks you have. Achievements page is visually bugged. Its been fixed for the next update. Thanks for the bug report.