About Stage Modes

Each stage has three modes: Campaign, Veteran and Spec Ops. You have to get three stars in Campaign mode to unlock Veteran, and you have to clear Veteran to unlock Spec Ops.

Veteran gives you one life, and only two available towers. You have to defend against six waves of elite enemies with only the towers available.

Spec Ops mode will pit you against one but massive enemy wave with only one life to spare. Fortunately, all towers will be available during this mode.