Castle Builder is a unique interactive type of online slot game that was developed by Rabcat. They designed the game to be highly interactive and entertaining in order to keep the players returning. The aim is to build ten castles in three different kingdoms by spinning the reels and gathering building materials. When a castle is completed a princess appears to choose amongst three suitors. This is the slots bonus game. Each suitor is worth a different level of prize and once she has decided on one, a wedding takes place and the respective prize is paid out. As every castle is completed the player also receives special achievements, or cash prizes, from the king which assists the player in moving up in ranking.