Ok, first thing is first:

M to mute, N to unmute
P to use, U to unpause
SPACE TO DE-SELECT

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.