Castle Assault is best described as a Living Card Game where Tower Defense meets RPG like Player advancement (your cards permanently improve) and plays in about 30 mins for 1 or 2 Players. 

Each Player controls a Castle on either side of the Battlefield with a Hero 'commander' outside of the Battlefield. Players play Units from their hand to the gameboard and these Units physically move toward the opposing Castle based on the Abilities of that Unit and your tactical Commands. Victory is achieved by bringing your opponent from 10 to 0 Health or destroying their Hero.