As for reference games, i havent seen any with this graphical style either, but the gameplay itself is based off of "tower defender" type games like the following:
http://www.addictinggames.com/strategy-games/clan-wars-game.jspBasically, your tower makes troops and so does the enemy AIs tower, each troop marches towards the others towers, engaging enemy troops along the way. When they reach the enemy tower, they attack it until the towers HP are zero. the first tower to zero HP is destroyed and looses.
