TanZen HD will recognize when the puzzle is finished. Features in TanZen HD that you won't find in the iPhone version: - Entirely new high resolution graphics! - 35 unique piece skins! Solve a page of puzzles to unlock each new design. - 5 different sand backgrounds. - Multiple save slots for family play. - Streamlined interface, with every option available from the main screen. - Larger play area for solving puzzles. - New puzzle picker layout, showing more puzzles per page. - Play songs from your own music library, right inside the game. - Left and right landscape orientation support. Other features: - Retina display graphics! - Over 500 puzzles for free! - Large, intuitive touch controls. - Solve puzzles in any order. - Hint system. - Puzzle memory keeps track of multiple, in progress, puzzles. - Puzzle reset. Give your device a hard shake to send the pieces back to the corners. - Track your progress, with a complete view of all your completed puzzles. - Advanced mode for expert puzzlers. - Soothing background music and sounds by Atomicon.