Half an hour with the instructions was enough to convince me that The Sentinel is the best BBC Micro game ever.
Its author Geoff Crammond wrote Aviator, probably the most realistic flight simulator on the BBC Micro, followed by the best racing car simulation, Revs.
He has produced an entirely new concept - have you ever heard of any other game where the basic unit of energy is the tree? Or even where three trees are worth a robot? The graphics are amazing. Three dimensional landscapes are generated through fractal routines, and they scroll faultlessly. There's also a very novel way of moving about and 10,000, yes ten thousand, different landscapes!
At the start you are only allowed to play level 0000, but as you improve you get secret codes to get to the others. Each level is made up of a landscape created from various hills, ridges, plateaus and valleys and you are given a 3D perspective view of this landscape from your current position. The idea of each level is to 'absorb' the Sentinel and hence try to defeat his evil influence in the universe.
You absorb him by seeing his base square, i.e. the square he is standing on. As he is normally on the highest point in the landscape, this is often not very easy. To gain energy, you can absorb the trees that are dotted about the landscape, but, as with the Sentinel, you must be able to see their base square. The only movements you have are to rotate left and right and to pan up and down. To move bodily, you must first create an identical image of yourself in the place to which you wish to move, which costs a robot (the equivalent of three trees), then transport into your new self. At this point you will be facing back towards your old 'shell' which can be absorbed to regain the energy you lost in creating your new self. To gain height, first build a stack of boulders (one boulder equals two trees), then transport into your new self. At this point you will be facing back towards your old 'shell' which can be absorbed to regain the energy you lost in creating your new self. To gain height, first build a stack of boulders (one boulder equals two trees), create your new self on top of this stack and then transport in the normal way.
During all this, the Sentinel doesn't just sit there like a stuffed lemon waiting to be absorbed. Oh no! He turns slowly on his pedestal trying to find you. As soon as he can see you directly, you are 'scanned' and energy begins to drop. You must either quickly find a place to transport to, or hit the panic button 'H' (hyperspace - it costs one robot) and you will re-appear somewhere random. If you do manage to transport, you must act quickly and absorb your old shell, as it will still be being scanned. This situation gets worse on later levels where the Sentinel is assisted by sentries, and then there are the trees that turn into meanies...
Playing for about three days, I've managed to reach level 0071, but I have a code for level 2044 (Send £10 to...)
Although the instructions are very complex, I thoroughly recommend The Sentinel to anyone - if you see it, buy it; if you don't see it, send off for it!