Design your own space invader games with Neil Davidson's DIY game creation utility

Over the years many variations of the space invaders game have been published for the Electron. However, none have contained a built-in editor to allow you to create your own waves of marauding aliens - but this version does!

Using the editor you can alter the existing invasion patterns, create entirely new ones, set the ferocity of the alien attack and their minimum attack height. What's more, you can also save your masterpiece and swap with friends' patterns, so effectively creating new games.

The opening menu offers of five options. If you simply want a game of Galaxy Invaders press the 5 key to enter the battle. Use Z and X to move your missible base left and right and RETURN to fire missiles.

If you manage to survive the ten waves of invading alien fleets and want a new challenge - or just want to reduce the difficulty level - select option 1 from the menu. You'll be asked which wave you want to edit - select from A to J.

The pattern that the aliens follow onscreen is displayed in a textual form. There are up to fourteen commands specifying a direction, such as up, down, left or right, and each command can be repeated up to 999 times.

The fourteen commands are labelled A to N onscreen so press a letter to edit a command. Now you can press L, R, U, D, A or N for Left, Right, Up, Down, Again (repeat the whole pattern again), or New (new alien). Press a letter to set the direction of travel, to send an alien back to the beginning or add a new one. Press RETURN when you have finished.

By typing in a three digit number you can now specify how many times this command is repeated. If you entered R for the direction, you could, for instance, enter 005 to make the alien move right five times. Press RETURN when you have finished.

After designing your alien wave pattern, press the SPACE bar. You will be prompted to set the start X and Y coordinates of the pattern, with 0,0 being in the top left hand corner of the screen.

When you have done this, enter the invaders' firing frequency at the prompt, followed by the minimum height below which they can't fire. This is to prevent them firing at point blank range, giving you little chance of dodging their bullets.

The final option is to set the number of aliens in the wave.

After passing on all this information you'll be taken back to the main menu. From there you can select Play and test your creation.

One potential problem is that if you aren't careful when designing the pattern the aliens can disappear off screen. For instance, if you set a starting point at the left hand edge of the screen and then tell them to fly left they will promptly disappear from sight - which won't be much fun to play.

Brush up on your mental arithmetic with this handy tester by Robin Langridge

MATHS MANIA is a short educational program for children aged seven years and upwards. It is designed to improve their mental arithmetic skills by providing a series of simple practical exercises.

The wide variety of difficulty levels built in to the program ensures that children of all abilities can make use of the program, but before moving on to that, your first task is to enter and save the program listing.

When you run MATHS MANIA you'll be presented with a menu consisting of four options: Addition, Subtraction, Multiplication and Division. On selecting an option you are then asked to enter the difficulty level, ranging from one (easy) to nine (difficult). Then you're on to the questions.

After each question you are told whether you answered correctly, and if not, the right answer is displayed and your running score is printed. After ten questions your final score and rating - ranging from pathetic to brilliant - is displayed. You are then returned to the main menu. From there you can choose the same topic again or a new one.

And that is all there is to it - a simple program that won't take long to type in, which is easy to use and provides sound practice with mental arithmetic.

Featuring stunning graphics and original gameplay, this fun educational game was written by Andrew and Stephen Weir for young children aged seven and upwards

The rich and famous mathematician Sir Addsumore accidentally washed his entire collection of rare and valuable numbers down the sink. So he called on you, the one and only owner of a yellow submarine, to retrieve his priceless collection before it is lost forever.

Your job won't be easy. Beneath the city lies a tangled network of pipes into which the numbers have been washed. You must guide your submarine through them first to identify and then retrieve the numbers one by one.

However, beware! Not all the numbers you find will belong to Sir Addsumore's lost collection.

Picking up the wrong number will have disastrous consequences.

To help in your mission, at certain points within the pipe network you will be told how to identify the correct lost numbers. So move carefully, pick your numbers wisely, and may the sea gods be with you.

Take care that you type in the program exactly as listed, with no extra spaces at the end of each line.

The program contains quite a large amount of machine code, and although encoded to save space, the listing is still quite long.

The simple answer is to delete all the data and assembler sections when the machine code has been set up.

This is automatically done by the program - so don't run it unless you have saved it, as half of it will disappear.