The Sentinel
Unusually for a game, The Sentinel didn't have a plot. A number of magazines did include a story in their review, but nowhere in the actual box packaging is a back story mentioned.
When the game loaded, the player was asked to input a landscape number from 0000 to 9999. After this, they were prompted for an 8 digit secret entry code, (unless they chose landscape 0000, which didn't require an entry code to play).
Before the game started, the player was shown an aerial view of the landscape. Each landscape looked like a greatly extended chess board, but with platforms of varying heights. The aerial view also showed the relative positions of the Sentinel (who stood on a tower at the highest point) and its sentries. Thankfully, the first few levels didn't have any sentries, thus giving the player a slightly easier introduction to the nuancies of playing the game. The Sentinel (and sentries in later landscapes) remained inactive until the player expended or absorbed energy.
The main concept of the game was all about energy. Trees and Boulders were dotted around each landscape. Boulders were worth two units of energy, whilst trees were only worth one. The robot controlled by the player was worth three. The player could rotate on the square they occupied and absorb the energy of any boulders or trees where they could see the square that those objects were standing on. Therefore, to absorb energy from something else, the player had to be on the same level or higher than the object. To move, the player had to create a robot on another square (costing energy to do so) and then had to jump into the new robot shell. They could then turn around and absorb the old shell and continue as before, assuming something else didn't start absorbing it first!
Once activated, the Sentinel and sentries also slowly rotated on the spot, scanning the landscape for squares which contained objects of more than one unit of energy. If they could clearly see such a square, the Sentinel or sentry reduced the energy 1 unit at a time. Therefore a robot would become a boulder, and a boulder would become a tree. Although the player could absorb trees, the Sentinel and its cohorts were obviously a little more environmentally friendly and would leave the trees alone!
If the player's robot fell under the gaze of the Sentinel or the sentries, an alarm would trigger and the robots energy levels would start to reduce as the energy was being sapped. The only way out was to move, either by creating a new robot shell or by performing an emergency hyperspace to a point anywhere on the landscape. The drawback with that strategy was that the player had little chance of absorbing their old robot shell and they might still fall into the deadly gaze of the Sentinel! Hyperspace also cost three units of energy (the number required to create a new robot shell) and if the player didn't have enough energy to complete the jump, then hyperspacing would destroy the robot and end the game!
The total amount of energy on each level would remain constant, so if the player was losing energy then for each unit they lost, a new tree (worth one unit of energy) would be randomly created elsewhere on the same landscape.
If the player survived and successfully absorbed the Sentinel, then an 8 digit code was presented. This code was based on the number of the landscape completed and the amount of energy left after the player hyperspaces to the platform where the Sentinel had stood. The landscape they moved to next would therefore be based on how well they had played the landscape (based on how much energy that had at the end). This meant that they didn't have to play all 10,000 landscapes to reach the end!
On the subject of the end, the only complaint that some players had was that the game didn't actually end! After completing the final level, the game returned the player back to level 000000 but with the access code equivalent to the energy they had amassed.
