Call of Atlantis: Treasures of Poseidon contains the original match-three and hidden object levels of Call of Atlantis as well as new match-three levels of the Treasure of Poseidon challenge mode. You choose which group of levels you will play.
As mentioned above, the Treasure of Poseidon levels are only match-three. You must swap two tiles to create a row of three or more of the same tiles. You must get pieces of that level's treasure to the bottom of the board to collect them and end the level. Each level is timed. Creating a row(s) of four or more tiles powers up the Amulent of Poseidon. When fully powered and then activated, it randomly destroys tiles on the board. You can also collect power items like the Bomb of the Titans, Lightning of Zues, Hourglass of Chronos, etc. that will help you. You can also use in-game gold to but these power items, if you wish. There are over fifty levels in the Treasure of Poseidon challenge mode.