Sudoku Grid Definition (SGD)
	define grid name
list item 1
list item 2
	define grid table
		define grid outer table (max. nr. of rows and columns) consisting of cells with both input and div object (?)
		assign CSS classes to cells to define:
			blank cell (i.e. not part of sudoku grid)
			input cell
				border style (combined with group definition - see below)
				background style (e.g. to show cell is part of diagonal group; to show value is either odd or even)
	define groups of cells
	enter fixed values
	log grid, group and fixed values definition in a format that can also be used as input for such a definition
compute: one step per change made
log every step of the computing process

Page consists of html and javascript
Some parts of html are fixed, other are created and changed run-time through javascript

Sudoku object
	Sudoku Grid Definition (SGD)
		method write_text_definition()
		method read_text_definition()
	groups = array of SudokuGroup object
		references to SudokuCell objects it contains
	cells = array of SudokuCell object
		references to SudokuGroup objects it is part of