Number Gulper is a gripping, fast moving game that helps develop arithmetic skills. The player has to build a number between 10 and 9999, by gulping numbers on a track on the screen using a manoeuvrable gulper, before its energy runs out. At higher levels there are scramblers which change the number if they are touched by the gulper, ruining any plans previously made.

The game works with both joystick and keyboard, and nineteen levels of difficulty cater for children of all abilities. Even adults find the upper levels testing! There is also a self test option to enable children to monitor the improvement in their mental arithmetic as they play the Number Gulper.

Number Gulper is a program which encourages children to practise number skills - addition, subtraction, multiplication and division - in an interactive game.

The player is asked to build numbers using only those displayed on the screen. As there are nineteen different levels in the game children of all abilities can enjoy a challenge using it. At the lowest levels, to add to the challenge, interfering scramblers appear which have to be avoided.

The game can be played using either a joystick or the keyboard controls.

There is also a self test option which enables children to check their progress in a more formal way.

First choose whether you want to play the Gulper Game or Gulper Self Test, press 1 or 2, and then the RETURN key.

Decide whether you want to play using a joystick or the keyboard controls, press 1 or 2, and then the RETURN key. (Remember: the joystick must be plugged into the 'analogue in' socket of your computer.)

Next you will be asked to type in the first number you want to make. This must be between 1 and 9999. If you have not played before, it is best to start with a small number, eg. 20. Type in the number, and press the RETURN key.

A 'board' now appears on the screen. In the top two black boxes, there are two important numbers, the MAKE number (which is the number just selected by the player) and the MADE number. The MADE number is selected by the computer and depends on the level chosen. The aim is to 'gulp' numbers on the track to change the MADE number until it is the same as the MAKE number.

Don't forget about the light blue ENERGY/TIME bar on the display. As a gulper moves around the track, and each time it gulps a number, it uses energy. You must change your MADE umber to equal the MAKE number before the light blue ENERGY/TIME bar disappears. (To do this, it often helps to plan your moves before you press the space bar to start your gulper off.)

In the black box in the centre there are three yellow gulpers, and on the red rtack are the numbers, each with a sign (+, -, * or /) next to them.

To start, press the space bar. The first gulper will move onto the red track. Move the gulper around the screen using the Z, X, * and ? keys (left, right, up and down) or the joystick. To change the MADE number, 'gulp' a number by pressing the space bar or the serve/fire button on the joystick when the gulper is over that number. If neither of these is done then the gulper will just pass over the number without gulping.

For example, imagine that you are starting with a MADE number of 5, and have to equal a MAKE number of 20. Look around the track and see what numbers are available for gulping. If there are 5+, 8+ and 2+ on the track, you can gulp each in turn to give a total MADE number of 20, and your gulper will get into the HOME base. Often, it will not be as easy as ths, for example it may be necessary to gulp 5+, 1+ and 3- in order to add 3 to the MADE number.

If you succeed in changing the MADE number into the MAKE number, the gulper goes in to the HOME base. If not, due to using too many gulps, or delaying too long in making the number, it disappears. In both cases, press the space bar to start with the new gulper.

If you get 2 or 3 of your gulpers home then you will be given a harder level for the next game. If you get no gulpers to the home base then you will be given an easier level to try. Your current level is shown at the bottom right hand corner of the display.

From level 3 onwards, scramblers appear on the track, which must be avoided. If a gulper hits one, the MADE numbe is randomly altered, and the gulper stops. You now have to rethink how to construct the MAKE number from the new MADE number. The game proceeds after the space bar has been pressed.

Note that when you gulp a division number e.g. 5/ it must divide exactly into the MADE number. If it doesn't, a 'NOT A FACTOR' message appears at the bottom of the screen, and you lose that gulper. To continue, press the space bar.

It is not possible to have a MADE number bigger than 9999. If you try to do this, a 'TOO BIG' message appears, and you lose that gulper. Equally, if you try to make your MADE number less than zero a 'LESS THAN 0' message appears, and you lose that gulper. In either case, press the space bar to continue.

If you decide on the self test option the first thing you have to do is type in the level reached in your last gulper game, and press the RETURN key. Now you are asked how long you think it will take you to do the test. Bear in mind while deciding that you will have ten problems to do. After typing in the time in seconds press the RETURN key to start. A problem will come up on the screen with the numbers having the same form as they had for the Gulper Game. Work out the answer, and type it in, followed by the RETURN key.

If the answer was wrong then it will be rubbed out, and you get a second attempt. If this is also incorrect the correct answer will be shown and a new problem is displayed. After ten problems have been completed the space bar symbol is displayed and when it is pressed the actual time taken is now displayed, along with the number that you got correct. After pressing the space bar again you will be returned to the beginning of the program.

Despite the incursion of calculators and computers into all aspects of life relating to numbers there is little doubt that the mental facility to manipulate numbers quickly and fluently continues to be of great importance to children and adults. This ability enables people to approach a numerical task with confidence either in the supermarket or at University, and gives them a head start over those who are not so skilled. With this in mind much effort is expended teaching number bonds and multiplication facts in school. Number Gulper has been designed to supplement this work.

Most children will arrive at Number Gulper with some simple mental arithmetic skills. The game encourages them to build on these skills in order to succeed and obtain higher scores. Many vital mathematical concepts are involved and constantly reinforced:

1. The relationship between addition and subtraction
2. The relationship between multiplication and division
3. That repeated addition is a possible method of solving a multiplication sum (but one which is highly inefficient)
4. Similarly, repeated subtraction is a possible but inefficient way of doing division

Other skills required include the planning and scale of operations to make the most efficient use of the numbers available on the screen. This is best done before the game starts and the most successful players will complete a whole range of mental number activities before they begin the game.

In field testing, this program has proved very popular with children of all ability levels in the primary school, as it combines the fascination of the fast interaction of the arcade game, with a strong educational content.