Android Demo

If your browser supports the video tag, below you will see a short movie of my first Android animation demo. Otherwise you will just see a boring text message. Let me know if this works for you; it seems an interesting new way of presenting features in my Android applications.

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Animation on Android

I wrote my first animation on Android! It is actually part of a simple screen tester, where I can inspect the screen size of a device and see different font sizes, colors, and text positions. For fun, I added three moving balls (the circles in the screenshot below), all bouncing between the four screen borders.

Checkers Move Coach

I received an email from Rein Halbersma who suggested an improvement for Checkers for Android by accepting a move as soon as any ambiguity has been resolved. In many cases this enables single click input. I have implemented this request, together with extending the "move coach" to show all valid moves, as illustrated below.

Hopefully this new option is useful for people that are learning checkers. Both improvements are available in v2.3 of Checkers for Android.

Board Gradient

Although I like the wooden board textures that I use for chess and checkers, I was never quite happy with the board texture I used for Reversi for Android (some called it a dirty pool table :-). Therefore, I am trying something new in version 2.3. Instead of using a texture, I use a radial gradient on the board, which gives the impression that the board has been placed under a lamp.

This new approach also slightly reduces the size of the binary. Let me know what you think.

Android 2.2

I am excited that Android 2.2 (aka Froyo) has been announced at Google I/O. Especially the Dalvik JIT compiler directly benefits all my game engines with deeper search. And yes, the 5x improvement reported for checkers in the Android 2.2 highlights page refers to Checkers for Android!

Replay Buttons

I am working on extending Chess for Android with full replay buttons. This will remove the somewhat arbitrary restriction of only an 8 half-move undo. Furthemore, it allows replaying older saved games and experimenting with different continuations.

Here is already a quick preview of the new landscape and portrait layout I am planning to use. Early feedback welcome!

Loading and Saving Games

I added a much requested feature to Chess for Android: the ability to load and save games (other than just the one in progress). To use this feature, long-press anywhere in the notation window to get to a menu for exporting the game to clipboard as PGN or FEN or, the new feature, for loading and saving games as file.

As illustrated below, after pressing "Save Game to File", a pop-up window asks the user to pick a file. Initially files are empty, but after saving they get marked with the date and time of the last stored game. Simply pick a marked file to overwrite or pick an empty file, as done below for file 3. Loading a game is done in a similar manner.

Perft for Checkers (again)

Today I was prototyping a distributed worker pool at work which needed some test input, and this gave me a good excuse to compute perft for checkers for depth 21 (one deeper than results I posted a while back). The perft breakdown per move (called "divide") from the start position for depths 18 up to 21 is shown below.

move divide(18) divide(19) divide(20) divide(21)
12-16: 550829166472 2517202147314 11531470109861 52945190026737
11-16: 566149929068 2564849953998 11736729175821 53527954221225
11-15: 435063007630 2041959240377 9515983205474 44775005468548
10-15: 472279451484 2180656975018 10055597639275 46574865098865
10-14: 402570639569 1859042884028 8600202424158 39822944739732
9-14: 441590753001 2068865301476 9698986164172 45530585259776
9-13: 625398758917 2881467090588 13406062152792 61923979665936
3493881706141 161…

Maze Solving in 6510

Not sure why, but I suddenly felt the strong urge to see if I could still program in 6510. So I implemented a backtracking solver that finds the path in a maze from the '-' symbol to the '+' symbol (actually an undergraduate programming exercise I did long time ago on a Motorola 68000). The result running on a Commodore 64 emulator is shown below. The active search path appears as white '*' symbols, dead end positions appear as '.' symbols.

And below the solution has been found. You can find the assembler source file maze.s (and a 6510 cross-assembler) on my Commodore 64 page if you are interested. You can define a different maze in the .byte section (just make sure the active search path length cannot exhaust the small stack of the Commodore 64). Also don't forget to remove the artificial delay to appreciate how fast machine code runs!

Commodore 64

Remember this screen?

Yes, that's right. I too became interested in computer science because of the Commodore 64. Although I still have my Commodore 64 somewhere, nowadays it is much easier to relive the good old times with an emulator, such as CCS64 (Per HÃ¥kan Sundell), VICE (the VICE team), or MP64 (an emulator under development by Michael Plet).

A while back I wrote a 6510 cross-assembler win2c64 that converts an assembler source file into a target file that can run on one of these emulators or, with some work, on the real Commodore 64 (an assembler converts human readable mnemonics, labels, and simple expressions into machine code; win2c64 is a cross-assembler because it runs on a Windows platform but generates machine code for the Commodore 64). If you are interested, you can find the cross-assembler and some sample programs at Aart's C64 page.

More Board Textures

Now that I am enthusiastic about textures, I also added a board texture to the other games. For Reversi for Android this hopefully also addresses complaints that the board was "too green".

For Checkers for Android, I simply reused the coffee table texture, as shown below.

Wood Texture

A user "dragonfish" suggested to add texture to the wooden chess board in Chess for Android. So I took a picture of my coffee table and used that as texture for the dark squares. See the result below.

Together with a minor engine improvement, this new feature has been released in v2.2.


I am now working for Topeka.

Copy to Clipboard (PGN/FEN)

Version 1.2.9 of Chess for Android will enable users to export a game to another application, such as an editor, email, or another chess program:

copy all moves to the clipboard as PGN (Portable Game Notation)
copy the position to the clipboard as FEN (Forsyth–Edwards Notation)

To use these options, long-press anywhere in the move list area. Then, the following menu appears.

Select one, then exit the chess application and go to the application where you want to paste the game. For example, I picked Copy Moves as PGN and went to messaging and long-pressed the text area.

Then Paste the contents of the clipboard into the message, and the game appears in PGN format (note that, for convenience, I use a slightly more elaborate algebraic chess notation than strictly required; readers should still accept that format though).

Likewise, using Copy Position as FEN, the contents would look as follows.

Opening Book

I added an opening book to Chess for Android. The opening book is small (slightly over 150 opening lines) and simple (transpositions are not recognized, unless the line is explicitly stored). Nevertheless, since the engine picks a matching line at random during the opening, the variety of play will increase. Version v1.2.8 (and onwards) supports the opening book, as well as a new copy-to-clipboard feature (more about that later).

While still in an opening line, the message "opening" appears at the position that usually shows the engine evaluation, as shown below.

One Star Ratings

I don't mind constructive criticism. Really, I don't. But take two recent one-star reviews for Chess for Android:

Stupid cant start a new game after youve lost
greg Fri, Mar 12 01:31:00 UTC 2010

This game cheats. Pawns shouldnt be able to capture pieces next to them and then move diagonally.
Eyal Wed, Mar 10 02:35:00 UTC 2010

Really, my game gets one star because you cannot find the menu button on your own phone, or because you don't know the en-passant rule (see also previous posting)? Please, if you don't like the game for a good reason, by all means give one star. But this?

Too Many Updates?!

While browsing through some recent comments posted on the Android market, I was surprised to read that some users complain that I am pushing too many updates. I usually work on these games in spurts, i.e. a lot of improvements in a short time followed by a period of relative quiet. Another problem is that the Android market does not enable me to push updates to specific platforms or builds only. So, for example, when I fix a bug for Android 1.1, some users will not see a change, but others may be happy to receive an update. Last, the Android market does not support a good way to show revision history.

Luckily not all users feel that way, as reflected in the comment:

Updates are a pain? Really? its wonderful when developers continually work on their FREE app to improve it. Be thankful not frustrated.
Vin Fri, Feb 12 11:47:00 PST 2010

Thanks Vin!

Android 1.1 Bug Fix

I always test new releases on emulators for Android 1.5 and higher (api 3 and up), for various screen sizes and other settings, as well as on the two actual Android devices that I have. However, I found out there was a bug on Android 1.1 (api 2), which I fixed in the latest releases of Chess, Checkers, and Reversi for Android. Users with an "older" phone that have never updated to more recent builds may have experienced problems (apologies for that!). The games should work again for all platforms. Needless to say, I added the Android 1.1 emulator to my mandatory release criteria.

Explanation of Levels

Since I just got some questions on the different levels in my Android games, I hope the following posting on this topic is helpful.

To change the level in either Chess, Checkers, or Reversi for Android, first press the Menu button on your phone, then pick the Level option, which gives you something that looks like the following screenshot.

Then select any of these levels. Here, Free Play means that the game engine will never compute a reply. Instead, the phone can be used as a "magnetic board" to study games or play a game up to a position for further play with the engine. In Random, the engine will instantaneously pick a valid next move at random. Pick this level if you like to win! The next Level 1 through Level 5 select different normal playing levels, increasing in both strength as well as time taken by the engine to compute its next move.

Finally, Chess for Android also has an Auto Play option where the engine plays against itself. After selecting this level, either make a…

Chess for Android Update

I just released a new version of Chess for Android that, like the previous updates of the other games, improves the text size on larger screens. On the Nexus One, for example, the notation window in previous versions was barely readable. This is now hopefully resolved for all current phones.

Next planned updates consist of adding a small opening book and an option to export a game to some external format.