From e2c84a5fd2b1ca6d3d8be0279466079b35b6c189 Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Sat, 30 Mar 2013 20:04:10 +0000
Subject: Introduce a mechanism in this source tree for building the container
 web pages for the Java applets. Previously, those have all been maintained by
 hand in my website's svn area, which is a bit silly. Now we have a file per
 puzzle in the 'html' subdirectory which contains the puzzle's name, one or
 two attributes, and the instructions snippet to go below the puzzle applet;
 and then there's a Perl script that builds all the real web pages out of that
 by adding in the parts common across all files: the header, footer, and
 middle fragment with the <applet> tag and resizing bits and pieces.

One piece _not_ checked in here is the footer text specific to my
hosting at chiark, which I think does still belong in the www area. So
Buildscr doesn't actually build the web pages; it just delivers the
bits and pieces by which my nightly snapshot script will be able to
run the program that _does_ build them, passing that footer as an
extra argument.

[originally from svn r9780]
---
 html/group.html | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 html/group.html

(limited to 'html/group.html')

diff --git a/html/group.html b/html/group.html
new file mode 100644
index 0000000..c0f52de
--- /dev/null
+++ b/html/group.html
@@ -0,0 +1,52 @@
+unfinished:Group
+<p>
+Fill in the grid with the letters shown to the top and left of it, so
+that the full grid is a valid
+<a href="http://en.wikipedia.org/wiki/Cayley_table">Cayley table</a>
+for a
+<a href="http://en.wikipedia.org/wiki/Group_(mathematics)">group</a>.
+<p>
+If you don't already know what a group is, I don't really recommend
+trying to play this game. But if you want to try anyway, the above is
+equivalent to saying that the following conditions must be satisfied:
+<ul>
+<li>
+<strong>Latin square</strong>. Every row and column must contain
+exactly one of each letter.
+<li>
+<strong>Identity</strong>. There must be some letter <i>e</i> such
+that, for all <i>a</i>, the letter in row <i>e</i> column <i>a</i> and
+the one in row <i>a</i> column <i>e</i> are both <i>a</i>. In the
+default mode, this letter is always <i>e</i> and its row and column
+are filled in for you; by reconfiguring the game using the Type menu,
+you can select a mode in which you have to work out which letter is
+the identity.
+<li>
+<strong>Inverses</strong>. For every letter <i>a</i>, there must be
+some letter <i>b</i> (which may sometimes be the same letter
+as <i>a</i>) such that the letters in row <i>a</i> column <i>b</i> and
+in row <i>b</i> column <i>a</i> are both the identity letter (as
+defined above).
+<li>
+<strong>Associativity</strong>. For every combination of
+letters <i>a</i>, <i>b</i>, and <i>c</i>, denote the letter in
+row <i>a</i> column <i>b</i> by <i>d</i>, and the one in row <i>b</i>
+column <i>c</i> by <i>e</i>. Then the letters in row <i>d</i>
+column <i>c</i> and in row <i>a</i> column <i>e</i> must be the same.
+</ul>
+<p>
+To place a letter, click in a square to select it, then type the
+letter on the keyboard. To erase a letter, click to select a square
+and then press Backspace.
+<p>
+Right-click in a square and then type a letter to add or remove the
+number as a pencil mark, indicating letters that you think
+<em>might</em> go in that square.
+<p>
+You can rearrange the order of elements in the rows and columns by
+dragging the column or row headings back and forth. (The rows and
+columns will stay in sync with each other.) Also,
+left-clicking <em>between</em> two row or column headings will add or
+remove a thick line between those two rows and the corresponding pair
+of columns (which is useful if you're considering a subgroup and its
+cosets).
-- 
cgit v1.1