Gameplay

The game is pretty simple; you simply need to prevent as many alien creeps you can can stop as possible (or better yet, let none escape at all) from crossing your checkpoint. You have four different towers in your arsenal, at least two heroes you can use at the same time, and two active abilities. You'll be facing waves and waves of enemies and on a standard campaign, have 20 "lives". On harder difficulties like Veteran and Spec Ops, you'll only have one "life" so you need to ensure that not a single creep gets past your defenses. These special modes also impose some limitations like having the ability to use only two types of towers. Completing a Campaign stage with no "lives" lost will give you three stars and unlock the next difficulty/ mode. Each map has three modes/ difficulty each.