Number Dragons is fun to play and has the most intuitive interface of all versions of this game. Also called Hidoku or Hidato: The goal is to sequentially fill a grid with numbers that connect horizontally, vertically, or diagonally. It is as challenging as Sudoku but is easier to learn. In every Dragon puzzle, you are given a grid with the beginning and ending numbers shown. A few other numbers are given as clues to how the A.I. solved the puzzle. Your goal is to complete the grid, finding the A.I.'s path or finding your own. One or more solutions are always possible. There are millions of unique grids. Number Dragons allows the player to undo moves, peek on the A.I.'s solution or start with a completely new game. Appropriate points are tallied as you play a 20-game set. Twenty-game sets are stored in a player's History to show their progress. Exceptionally high scores can earn you a place on the "Legends scoreboard", maintained on the internet. Additional game levels are provided to challenge the player. Even the 4x4 grid can be challenging, and additional points are given for faster gameplay. The higher levels 5x5, 6x6, 7x7, 7x8, 7x9 and 7x10 can be extreme. Working your way through the levels can train your mind to develop some standard and unique strategies for path discovery. Solving puzzles can be fun, satisfying and challenging.