20 sec is too short. Lag can kill you easily. After you beat the campaign mode, the computer mechs become WAY too powerful (unless of course you pay to play). Was fun for about a week, but I'm going to abandon ship now.
You spend too much ammo just to have it lag when you're almost done with a level over and over again. Then you get like no money and you're basically screwed. Try fewer but harder zombies. It lags when there are tons of zombies. As is, you have a great game, but you can't really win. Zombies kill you while you're just frozen near the end of each level.
Can't you fix the lag for the love of god? The game just continues to play long after I've given up. I can hear my gun still shooting, but there is no hope of controlling anything.
 "Awesome Tanks 2"){kind=icon}
 "Supermechs"){kind=icon}
 "Galaxy-Siege2"){kind=icon}
 "Galaxy Siege 3"){kind=icon}
 "SAS: Zombie Assault 4"){kind=icon}
 "SAS Zombie Assault TD"){kind=icon}