The catch is, there are 4 types of attack, and 4 types of bad guys, each type of bad guy can only be killed by 1 type of attack. player will have to remember which bad guy is weak against which attack. and when the wave is getting faster, more and more bad guys with different weakness will make player lose focus which bad guy is weak against which attack.

Best iPhone Air Cases – 17 Cases Tested!
The iPhone Air presents a unique challenge for case manufacturers: how do you protect an incredibly thin phone without defeating
