My Android app Senior Chess

Senior Chess is an Android application based on my chess program Queen (running under Windows). Besides playing chess games in the default Play mode, you can also use the Edit mode to set up positions and let Senior Chess search for the best move. You can read positions given as files in the well-known FEN format, and you can also save positions to open them later. A game can be saved in the standard PGN format so it can be opened later. If internet connection is available, Senior Chess will find the best move in any endgame with at most five pieces (and in some with six pieces) on the board. This is possible thanks to online Nalimov endgame tablebases, made available as a webservice by Lokasoft. The app does not use internet connection for any other purpose. This video shows both how to set up a position in edit mode and how Senior Chess finds the right move in an interesting endgame with a single pawn, also indicating in how many moves the defending king will be mated. To get an idea of the sometimes daring and even hazardous style of chess playing by Senior Chess, just have a look at this game.

Senior Chess is available for free at Google Play Store Here is a video of a game, with strength level 1 s set for Senior Chess, playing Black.

Here are some tips about the commands available in the options menu:

New game
This introduces the start position, but you should be aware that it does not reset some other settings, such as thinking time and view of the board.

Undo last move
This command goes back a full move, that is, a half-move for each side. There is no special command to redo this full move.

Switch sides
If, for example, you play White, this command will make the computer play White and you Black. This is the case in Play mode. In Edit mode, discussed below, the name of this is Change side to move. A red dot in a corner of the board indicates the side that is to move.

Go (machine to move)
In Play mode, this is similar to the previous command: you can use it to make the computer, instead of yourself, make the next move. In Edit mode, you use this command to switch to Play mode and let the computer play the next move. This Go command is also useful to go back to normal Play mode after using Only user moves mode, as discussed next. When the machine is 'thinking' this command is temporarily replaced with the command Move now (stop thinking), as discussed below under Level

Only user moves
This command is useful when, in some postion, you want to make some moves for White and Black yourself. Use the Go command to go back to normal Play mode.

Edit mode
This enables you to set up any position. You can move pieces on the board as you like, adding pieces to the board and removing them. The latter can be done either by moving them to the row of pieces shown below the board or by clicking twice on a piece. When you go to the edit mode, you have to choose between starting either with the current position or with an empty board, the latter being useful to set up endgame positions. As discussed above, the Change side to move command can be used in this mode. To be able to end the edit mode, the command text Edit mode has temporarily been replaced with Leave edit mode. After leaving edit mode, you can either make a move yourself or use the command Go (machine to move)

This opens the sub menu with the four commands Open position, Save position, Copy position to clipboard, and Paste position from clipboard. They are all based on the well-known FEN format, an compact and elegant way to define a position as readable text. Version 1.63 and higher also offers the two commands Test position, selected at random and Test position, selected by number. There are (a) 300 test positions taken from the well-known test suite WAC, published in the book Win at Chess by Fred Reinfeld (1958, 2001), Dover Books on Chess, and (b) 100 endgame positions. The latter are a subset from those found here. You are encouraged to find the best move, which is visible in algebraic notation during a few seconds when the position is loaded.

This introduces a submenu with the commands Open game and Save game, both based on the well-known PGN format. After opening a game from a PGN file, first an animation of the game is played. You can stop this animation by using the Stop movie command of the options menu (where it temporarily replaces the Undo last move command, discussed above). Then you can view all moves of the game and their resulting positions, traversing the game by going backward and forward through the game. In version 1.78 and higher, you can do this by touching buttons displayed below the board. While doing this, there is a command Use current position to play so you can end the traversing mode. After this, you can either make a move yourself or use the command Go (machine to move).

The chosen level applies to the time the machine 'thinks' for each move. You can think yourself as long as you like. The level can be changed during a game, even while the machine is 'thinking'. This is important in connection with the Infinitely long thinking level. You can use this level to see how long it takes Senior Chess to find the best move in difficult chess problems. During thinking the best move found so far is displayed, along with a score. When you want the machine to end thinking and make this move, use the command Move now (stop thinking), which replaces the command Go (machine to move), discussed above, as long as the machine is thinking. In version 1.59 (August 2014) and higher, it is possible to let Senior Chess occasionally make weak moves, so that low- or moderate-level human players have a chance to win. Such moves are also known as odd or handicap moves. Odd moves are usually very weak ones. You can set the frequency of odd moves as you like. After selecting the level Possibly weak moves..., the user can specify the percentage of machine moves that should be such odd moves. After entering 100, all moves will be odd moves, which enables even absolute beginners to win. If you win too easily this way, use a lower percentage, such as 25, causing about one out of every four moves to be an odd one. Here is a video to illustrate this.

Use this to rotate the board. Using this command when you are viewing the position from the usual perspective of White, you will view it from the viewpoint of Black, and vice versa.

This shows both a version number and a link to this web page.

About the word Senior in the name
The word Senior refers to myself, not to the users of this app. The other day, my son gave me an interesting Dutch book about the brains of seniors, just when I was desperately trying to find a suitable name for my chess app. Having programmed for more than 50 years, I don't exaggerate when claiming that the app was written by a senior. I might as well mention that as early as 1960 I passed a programming test, a certificate of which was handed out to me and signed by Dr. Max Euwe, who was the head of an institution in Amsterdam that had to do with programming, as you can read in this web page about Euwe, containing the sentence He was appointed director of The Netherlands Automatic Data Processing Research Centre in 1959. Euwe was a very well-known Dutch grandmaster and World Chess Champion from 1935 to 1937. So much about the word Senior in the name, which I hope will not frighten away any potential users younger than myself.

Leen Ammeraal