Have you ever tried to imagine a new game idea? It's not easy, as the paucity of different games on the market attests. Consequently, a recent package from Krell Software caught my attention. Before I tell you about it though, let me tell you *my* fantasy of how it was dreamed up.

The software department guys 'n gals are sat round having a brain-storming session. "How about a skunk having to cross the road?"... "No, Loudon Wainwright III has the dead skunk market sewn up." "Well, how about having to shoot down... no, I guess not."

Suddenly, a quiet voice from the back says: "How about a game based on the spread of the plague?" Total silence for almost a minute, then the suggestions for Frogger clones slowly start to be made again.

I mean, talk about going down like a lead balloon, who would imagine Black Death? Well, someone did, although the Krell style involves not crediting authors.

Yes, the scourge of the 14th century can now be yours in the comfort of your own living room... or is that dying room?

Black Death simulates the spread of an epidemic through a population, with players fighting the spread by choosing strategies for innoculation.

It is not just a game, though. The manual claims it is designed to teach basic principles of epidemiology and public health decision-making.

The game starts with an instruction to read the manual, not because the controls are complex but because the underlying model needs to be appreciated.

If you are going to change any of the parameters from their default values it helps to know what you're doing. Next is the option to change the parameters, with the default values being displayed.

For example, if you'd like to increase your chance of success, you may want to decrease the contagion probability from its default value of 0.8.

If you think your hypodermic isn't too clean you may want to increase the probability of a fatal innoculation from 0.05.

When you've done all that you might as well make a medicinal cup of tea because the program then takes just over two minutes to fill the text screen with a 39 x 19 matrix of 0s, 1s and 2s.

These represent the population, with 0 signifying a well person, and the numbers 1-9 signifying increasing levels of sickness. After 9, the + sign is used to indicate death. Vaccinated people are represented with a * and recovered people with a !

Now it's your turn, with up to five innoculations or five therapies possible, administered by using I-J-K-M to move a cursor to the patient and using V to innoculate or T to therapise.

Up to six players can participate, each having a supply of vaccine, so you can develop group strategies if you want, and there's a save game facility if you can't finish in a single session.

Once each player has "moved", it's the infection's turn. Each number on the matrix is updated depending on the state of its neighbours and the various probabilities.

This takes a little less than the original two minutes, although it still slows the game down somewhat.

Numbers 0, 1, 2 and 9 are displayed normally 3, 4 and 5 are displayed flashing and 6, 7 and 8 are displayed inverse. This means that after a few turns there is an awful lot of flashing on the screen which I found distracting. It also makes the flashing cursor difficult to locate at times.

There is an alternative display in colour on the graphics screen, but trying to make sense of it in monochrome was impossible. Even in colour, trying to remember what each colour stood for once the display became complicated was not easy.

Three other factors detract from the colour display. Firstly, there is no cursor visible so any movement *must* be done on the text screen. Secondly, unlike the text screen, any action taken does not appear immediately - the graphic display is only updated once each reporting period.

Thirdly, the movement to graphics seems to use the equivalent of POKEing -16302, so that the status text no longer accompanies the display. Why not use -16301 and use a mixed mode? Effectively, then, the colour display is a pretty picture to look at between bouts of playing the game.

So what happens when the game ends? Unfortunately I can't tell you, because I've never managed to get that far. The original disc supplied for review had a bug which caused the game to run indefinitely.

Krell were very prompt and efficient in providing a replacement, but it seems to have the same problem.

I think Black Death is a good idea but not very well implemented. It is very slow because of the updating required between moves, and the problems with the disc are obviously more than one-off.

You notice how I've resisted the temptation to say that the game is "plagued" with difficulties?