Aegis is the in development title of Dusk Software's upcoming tower defense variant. Gameplay will focus on deck building between maps to prepare and setup which towers and effects are available in game. Cards are acquired through in game currency awarded at the end of maps as well as drops from boss creep.
While the game is still in an alpha stage, the website has been opened up to donations and we've received more than a dollar, so I think that counts for the challenge :)