This is a nice Sudoku version. Clean screen, allows for pencil marks. Playable in landscape or portrait. In portrait mode, you switch between final and pencil mark "keyboards." In landscape, they are both visible. It has seven other variants. 10,000 available classic games, and 5000 variant games, ranging in difficulting from Very Easy to Easy, Advanced, Hard, Very Hard, Fiendish to Nightmare.
You can customize how inputting the numbers work, to some extent--tapping the cell first then the number, have a pop-up appear, you can undo moves. There's a color mode for use in solving. When you enter a number in a cell, all of the other cells that are already filled in with that number will highlight. If all nine possibilities are filled in, the number on the keypad highlights so you know you don't need to solve for that number any more. (Same with the pencil mark keypad.) If you press and hold on a cell, the row and column it is in will highlight for you to double check that the number you're going to enter isn't already in that cell.
You can pause a game, and re-enter later at the same position. You can have multiple games started and choose the one to go back to by tapping on "Play Sudoku" on the main screen and then tapping on the "Playing" screen. Or tap on Resume Sudoku on the main screen to go back to the game you were last playing. Undo status is saved with the game. You can bookmark the game at various stages if you want to save a position and return to it in case you go down a wrong path solving the puzzle. It has incremental hints. It will give a broader hint and then narrow down the cell you should look at before giving you the actual number. This adds to your time. (Yes, it times you although you can turn that off in Settings.) You can restart a game. You can switch the game in landscape mode so the keyboard is on the left. There are a ton of other customization options.
This is an attractive, clean sudoku. No little gimmicky graphics, a very spartan display. No music. Lots of games available, and you can apparently import more. It is playable in airplane mode. I give it five stars.
These apps are compatible with the original Fire and with my Fire HD 8.9" 4G. To tell if an app works for your Fire HD or other Android device registered to your Amazon account, click on the above link and look on the right side of the web page. Amazon will tell you if it will work with your registered device.
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