Basically the units can either control themselves or you can comandeer one in order to get money for kills and combos etc. The aim is to stop the enemy units from entering your toy box.

Took a quick peek at the gameplay and it looks fun. Love tower defense... this is a tower defense game, right? Judging from the video it looks like it, but I'm not so sure, it seems so vague for me because of how you can zoom in and control the unit.