The trick with the elevators is not to have one long one, but several smaller ones. Build a five story elevator, then start another one on the same floor (don't upgrade the last one). I did that - didn't have any complains about elevators in a 20 story hotel. Tried adding one one long elevator at the end, and EVERYONE was giving out - so i destroyed it - which made everyone happier...
"DEVELOPER RESPONSE FROM IRIYSOFT
Flying enemies appear from the direction which is opposite to the base. They target towers so they always fly where your towers are."
- That's a lie: in Level 8 they come from the same direction as the base.
The game is more luck based than a fun game should be. When you see your opponent having armies of 100+ units and you're making only 29 (plus fighting against another opponent) - there's no strategy that can beat that. I have no desire to play this game anymore.
The game is unbalanced: if you use legionary (+1 upgrade to spawn), archers (+1 to spawn) and peasant (+2 to speed) then you can win the game without any other units.