The Sentinel game tribute page

BBC Micro


The Sentinel was written by Geoff Crammond and published by Firebird in 1986.

What makes this game really great is a stark mood that makes it really engaging. Once you understand how things work it gets very addictive.

I have one tip: the more energy you collect the further you will go to the next level. So before absorbing the Sentinel make sure you absorb all trees in the field.

I am ambivalent on which version is the best between the Amiga and the BBC Micro. The Amiga is prettier and it has nice music by David Whittaker. The control is a little fidgety and made me loose quite a few time. The BBC Micro version is a lower resolution but the controls are much sharper. Too bad it doesn't have music ;)

There was a PC release called "The Sentinel Returns". It had flashy graphics but I didn't like it much. It had a huge flaw: you couldn't tell which way the sentinel is facing!

There have been a few remakes but none match the original. The best one is Georg Rottensteiner's remake. However, the mouse control doesn't quite recapture the original.

Sentry is a remake with 3D mode for red/green glasses. I found it completely unplayable.

Zenith is a remake by John Valentine. It's too bad the control keys are really awkward. Switching between the arrow keys, A Q B and R is just too difficult. Otherwise it looks very nice.

There is even a flash version which is just a proof of concept. It's on my maybe-to-do list to do a proper port of this game. It would have smooth graphic but retain the original feel and control which are fine. I would have to disassemble the algorithm that generate the terrain. It would be nice to know some assembly...

I have included some of the code to get to further levels. Interestingly the code are different between platforms.

BBC Micro

This is the original by Geoff Crammond.

0022 79066357
0060 95647539


Note that if you don't have a c:\ drive or you wish to install sentinel elsewhere you need to do this extra step. After loading the Amiga 500+ configuration click on Hard drives. Click on properties and adjust the path. Don't forget to save the configuration.

0011 40556356
0035 14767076
0069 83219410
0103 36873128

Press CTRL+F12


This is the one that I used to play in the 80s. I have included it for nostalgia's sake. It was a rewrite by Mike Follin.

0022 88670629


The object of the game is to absorb the Sentinel and replace him as ruler of the landscape. Once achieved, you may hyperspace into a new world to begin the struggle afresh.

Once you have loaded the game, the title screen will be displayed. Press any key and you will be asked to input a landscape number from 0000 to 9999.

After you have entered the landscape number and hit return, you will be prompted for an 8-digit secret entry code, unless you choose landscape 0000, which does not require an entry code.

After a short delay you will be shown an aerial view of the selected landscape which shows the relative positions of the Sentinel standing on the tower and the Sentries, if any. Pressing any key will take you onto the landscape's surface. The Sentinel and sentries will be inactive until you expend or absorb energy. This allows you to have a look around and plan your assault on the Sentinel.

Once activated, the Sentinel and Sentries slowly rotate, scanning the landscape for squares which contain more than 1 unit of energy. If they can clearly see such a square, the Sentinel will reduce the energy to 1 unit by absorbing 1 unit at a time and creating a tree randomly on the landscape. Therefore a robot becomes a boulder and a boulder becomes a tree.

You absorb things and create things by turning on your sights and centering them on the square surface below the objects to be absorbed/created. Boulders, however, act as an extension of the square surface, and sights should be aimed at the side of the boulder. Boulders can be stacked and have things placed on top of them.

The amount of energy you have is shown at the top left of the screen in the form of Robot, Boulders and Tree icons. A yellow Robot icon is worth 15 energy units.

To move around the landscape, you must create a Robot and then, with the sights still on, press the transfer key. You will now be in the new Robot, facing your old Robot, which you can now absorb.

The indicator on the top right of the screen is the scan warning. If a Sentinel spots you, this indicator will be filled with specks. You have about 5 seconds to move out of view before your energy is drained 1 point at a time. Once all of your energy has been drained, then you have been absorbed and the game ends.

The total amount of energy in a landscape remains constant, so if a unit of your energy is absorbed, a tree will be randomly placed on the landscape.

If the Scan warning indicator is only half-filled with specks, this means that the Sentinel can see you, but cannot see the square that you are standing on: so it cannot absorb your energy. In this situation, it looks for a Tree near you and transforms it into a Meanie.

The Meanies' job is to flush you out, which it does by forcing you to Hyperspace. The Meanie rotates quickly, making a low clicking sound, until it can see you. You will then Hyperspace to a new location.

Hyperspacing effectively wastes 3 units of energy, because it creates a new Robot in a random position and automatically transfers you to it, leaving your old Robot behind. You are likely to end up at the same height or lower but never on your original square. If you Hyperspace will less than 3 units of energy, you are destroyed.

Once the Sentinel has been absorbed, you can no longer absorb energy, although you can still create objects and transfer to other Robots.

Once you Hyperspace, while standing on the Sentinel's tower, you will be given the 8-digit entry code for a new landscape. The landscape that you are given = Present landscape number + Energy after the Hyperspace.


Pan left        S         Hyperspace      H
Pan right       D         U-turn          U
Pan up          K         Absorb          A
Pan down        M         Transfer        Q
Create Tree     T         Quit            BREAK
Create Boulder  B         Pause           P
Create Robot    R         Unpause         ENTER
Sights on/off   SPACE     Music on/off    Z


Tree    1       Sentinel  4
Boulder 2       Meanie    1
Robot   3