TOWARDS the end of 1986 that rarest of rarities, an original game, was released by Firebird. Called Sentinel, it was the latest masterpiece by Geoff Crammond, who earlier had proved that the BBC Micro could support top class software with such efforts as Aviator and later the excellent Revs, still regarded by many as the definitive driving game.

Sentinel consists of 10,000 landscapes, each containing a Sentinel and up to six Guardians whose life energy you must absorb before gaining access to another landscape.
Each landscape is rather like a contoured open plan chess board with valleys, mountains and plateaux on which trees abound. The key to the whole game is energy. The smallest unit of energy is a tree; boulders are worth trees and Sentinels three.

Sentinels are like giant Oscars that slowly rotate on their elevated platforms. Whenever a Sentinel, or Guardian, turns to face you, it begins absorbing your energy, randomly redistributing it throughout the landscape in the form of trees.

The only way you can absorb the energy of the Sentinel, of its Guardians, is by reaching an elevated position in the landscape from which you can look down on its platform.
You can only absorb an object's energy when you can see the square on which it stands. You start each level in the lowest point of the landscape, often only able to see the tops of a few trees and the Sentinel towering above you.

Getting high enough to be able to absorb the Sentinel is in principle simple, but far from easy in practice. Imagine you're standing on the ground with an empty square beside you. You can create a boulder on the empty square. Then, on top of the boulder you can create a "copy" of yourself into which you can transport.

You're now standing on the boulder looking down on the 'old' you which you can absorb so as not to have lost any net energy, except that tied up in the boulder.
From your new vantage point you can see bits of the landscape visible because of your extra elevation. You may already be able to see the bases of a few of the trees the tops of which you saw earlier. If so, absorb their energy, you're bound to need it later to create more boulders.

And you're not limited to just building one builder at a time either. Apart from the fact that each one costs two units of energy to create, there is nothing stopping you building a tower of boulders before placing yourself on top. But although it allows you too make big jumps in height, having so much energy tied up in boulders proves to be too risky a strategy.

As soon as a Sentinel or Guardian starts sapping your energy you have to transport to a safe part of the landscape or risk premature death. This means leaving behind all the boulders. Although from your, hopefully, safe point on the landscape you can begin reabsorbing the boulders, you are now competing with the Sentinel which, even though you've moved, will still absorb any other energy source it sees.

Frequently, a policy of little and often is the key to success. Move from place to place, always staying one step ahead of the Sentinel, without ever having too much capital invested in boulders.

Compared with earlier 8 bit versions and the ST conversion released late last year, Amiga Sentinel, programmed by Steve "Goldrunner" Bak, is faster and has been given a complete sonic overhaul in the form of an incredibly atmospheric set of eerie, almost surrealistic, sound effects and musical cameos courtesy of David Whittaker.

Although the lack of effort put into Amiga conversions is often disappointing, Firebird has wisely decided to stick closely to Crammond's original 8 bit graphics, although they are brighter and crisper than in previous versions.
Any attempt at major modification would have been a big mistake, purely because the original was so perfectly crafted.

If you've never experienced Sentinel, treat yourself to the nearest thing yet to the perfect game. Unless you're an out and out death merchant you won't be disappointed.

Even in its 8-bit incarnation, Geoff Crammond's avant-garde game was a rare example of strategic gameplay on a par with chess. Here was a game which could take literally years to complete. With the release of 16-bit Sentinel, originality is now a rarity everyone can afford. You are a lone synthoid doing battle against an all-seeing Sentinel and its minions, the Sentries. Pure energy is the medium of progress in a series of tactical decisions where you must gain sufficient height to be able to absorb your enemies.

In the two years since the Amiga became something of a household name, there has been very little original software produced for it. A few software houses, like Psygnosis and Cinemaware, deliver the goods, granted. But on the whole the Amiga's software base seems to consist generally of conversions from 8-bit games, which are then tarted up a bit.
Geoff Crammond's The Sentinel falls in the latter category. However, it is also undoubtedly one of the most original concepts ever to appear on any computer. The 64 version was praised to the skies when it was released over a year ago, and I am about to do the same to this latest incarnation. The Sentinel on the Amiga is not vastly different, but there are a number of nifty enhancements. But just in case you missed out on all the fun the first time around, here is how it works...

There are 10,000 levels to play, with the objective of completing them all. Each level comprises a chequered landscape (a bit like a contoured chess board really) with trees dotted around. You control a being called the Synthoid and start at the lowest point on the landscape, with the aim of overthrowing the Sentinel who occupies the highest point. You move around by creating a new robot shell and transferring to it. However, you can only create a robot if you can see the square on which it is to sit. Meanwhile, having sensed your presence, the Sentinel turns around on her plinth, scanning the landscape. Should her beady sensors fall on your frail form, she will drain energy until you die. Obviously, a good strategy is the order of the day.

Extra height is gained by creating a boulder on which to place your new robot shell. Again, you have to be able to see the square in question. The Sentinel does not like you stealing it from her landscapes. So you have to ensure that once you have transferred you absorb the old shell to keep up your energy level. It is worth sucking up any trees while you are at it. The trees are the basic unit of energy. A boulder is equivalent to two trees, and a robot is worth three.

So what of the improvement? Well for a start, this version is considerably faster than any other and I do not just mean the speed of the graphics; the whole pace is extremely fast and is guaranteed to induce sheer panic into even the hardiest player, it is also more colourful than the 64 version, and there is an odd David Whittaker soundtrack playing throughout. I am not so sure it enhances the edge-of-the-seat atmosphere, but at least you can turn it off and just have the sound effects.
But these enhancements are purely cosmetic. The most innovative improvement is the fact that you can play with the mouse in conjunction with a few keys, rather than just using the keyboard.

Not so neat though is the HELP function. Pressing the HELP key when the cursor is pointing into the sky results in a map of your surroundings being displayed. This seems detrimental to me, as what makes the Sentinel so absorbing to play is the nail-biting, nerve-wrecking tension of not knowing where anything is. Mind you, you do not have to press HELP, but it does seem a shame that the option exists.

The Sentinel is simply a classic concept, and this version is the best yet. I cannot praise it highly enough (heaven knows rating something like this is hard enough), so I will just say: BUY IT!