Space Invasion Tower Defense - Build 12 kinds of towers to defend against invading spaceships in 2 game modes. In the first mode, prevent all the ships from reaching the bottom. In the 2nd mode, protect the gem at the center. This is not a build your own maze tower defense game, it is different from that. You only have 5 gems of which you can build ultimate towers with. Instructions: Drag and Drop towers. M to mute, N to unmute. P to use, U to unpause. Space to de-select.