HTTP-Othello

The complete state of the game is encoded in the URL after the "/" character. This means that no information about the state of the game whatsoever is stored at our WWW site. Also, you can undo moves with the Back button of your WWW browser. Your browser may even indicate which move you took last time in the same situation.

What's in that URL ?

The "/" (and everything before it) is not important.
The first digit after the "/" is either 0 or 1:

0 Human player plays black (black makes the first move).
1 Computer plays black.

The second digit contains the playing level.

All subsequent characters denote the moves that have been played. Every pair of characters denotes one move. The first character of a pair indicates the color of the player, this character is either a "+" or a "-":

+ Black played the move.
- White played the move.

Normally the "+" and "-" moves alternate, unless a player could not make a move at some point.
The second character encodes one of the 64 fields of the board. The encoding method is rather awkward.
In all WWW browsers it is possible to edit the current URL. In this way you can undo several moves, or force my program to play moves that the move-evaluator would never select. If you add an illegal move to the list, the program will signal this.

The fields that are legal to play trigger an URL that adds one move to the list. Most WWW browsers show the URL of an anchor when the cursor is positioned over it.
The fields that are not legal to play trigger an URL that explains that that field can not be played and how playable fields can be recognized.

Random moves

In some cases the move-evaluator of my program finds several moves that are equally attractive. In such cases it makes a random choice. If you use the Reload button of your WWW browser, the program may select an other move, thus not producing the same screen. This is a feature, not a bug.

No legal move - forfeit

When the program detects that there is no legal move (and the board is not full) the other player gets another turn. If the other player cannot play either, the game ends.

If the program plays a move after which the human player must forfeit, the program makes another move (after which it is possible that the human player must forfeit again. The program continues playing until one of the following is true:

There is again a legal move for the human player.
The board becomes full.
There neither player can make a legal move.

In the last two cases the game ends.

The graphics

The board is built up using four different graphics files:

A white empty field (can not be played) (may not be visible on your screen)
A dotted empty field (can be played)
A field with a black disk
A field with a white disk

The graphics were created with MacDraw 2 on an Apple Macintosh computer and later converted to ".gif" files. All WWW browsers detect it when the same graphic image is used again. Therefore those four images are usually transmitted once.

Because the fields are used as anchors (pointers to URLs) the WWW browser draws a (usually) light blue line around it. The thickness of this line may vary with the particular WWW browser. To prevent any problems with the alignment of the fields, all fields are anchors, even those that do not represent a legal move.
All non-playable fields contain the same anchor. Therefore when you've clicked once on an unplayable field (and got the "This is not a legal move" message) those anchors will suddenly all have the color for a followed link (usually a dark blue line) around them. This highlights the legal moves even better.