Tesselations is an extraordinary program, a first in the home computer league. Its educational content goes from the mathematics classroom into the art and design department and beyond. The program is flexible enough to attract all sorts of users and friendly enough in terms of operation not to disappoint them.

To quote the manual, "Tesselations can be used to generate tiles which always fit together so that they can be tessellated across the plane of the screen." The program Tesselations can produce, for instance, any pattern from the Islamic, Chinese, Celtic or Japanese cultures, or any other come to that. Consider the pattern on your lounge or bedroom wall. Tesselations can reproduce it and any other such interlocking pattern.

The program employs a new form of "human interface" designed by Fred Daly of Homerton college. Four keys, the cursor left and right, Return and Space Bar do the lion's share of all the choosing and actioning which goes on during any session with Tesselations. The bottom of the screen presents the user with choices, each represented by a single letter (T for tesselate, R for rotate, L for library and so on).

It's a form of menu for each part of the program but a very economic and efficient one, easy-to-learn and quick to implement. I had my doubts about it at first and wondered why the good old function keys had not been used. No key strips needed: all the information is on screen and the excellent manual takes you through every stage as if you had just seen your first computer keyboard.

There are four main routes out from the main menu. The library accesses all disc information, catalogues, saves and recalls library files. The drawing route allows you to create your own pattern on a single tile. Drawing allows you to change the colour and shape of the tile edges, to draw within the tile and to erase the current drawing. Drawing within the tile encompasses all seventeen groups of plane patterns. These involve rotation, reflection and glide reflection symmetry. If you don't relate to the mathematical terms then this program will explain them in a highly visual manner.

The tesselation route does all the work, the 6502 number crunching away until the screen is full of your original tiles. You may not be able to make out the original pattern so there is a facility to overlay the tile outlines. The scaling can be changed in the range of 0.2 to 1 of the original size and continually experimented with, recalculated and displayed.

The frame option presents the choice of rotating, side stretching and corner stretching your tile shape. A correct description of the shape, e.g. Square, Rectangle, 60% Rhombus is displayed.

The printer option can be called upon by getting back to the main choices and hitting Copy. It has been tested with Epson MXs, Walters, Integrex colour - very impressive, and Epson RX-80. When tried with an Epson FX-80, another popular option with the BBC, it did not perform.

Tesselations is a very special program for many reasons. It packs more performance into an educational program than any other BBC program so far. Its applications are very wide ranging, from crystallographers to home economists. It is very easy to use despite the considerable flexibility and number of options.