Geoff Crammond‘s The Sentinel (aka The Sentry in North America) is a strange chess-like game where you have to sneak up on an overseeing watcher, who is perched high on a platform, overlooking the play area, and absorb him before he does the same to you.

To move you must be able to see the top of the space on the landscape that you want to move to. And to be able to see the higher areas of ground you must absorb trees to increase your energy reserves, and stack boulders, which you can then teleport to and stand on to raise yourself higher.

The ever-present risk is that you must avoid the gaze of the rotating Sentinel itself (possible by hiding behind the landscape or staying out of its direct view), and also avoid the gaze of its deputies (there are other sentries dotted around on some levels).

The Sentinel was a critical success when it was first released in 1986, and is seen as a classic video game now. It has 10,000 procedurally-generated, seeded levels, all but one of which require an eight digit number to access.

This is definitely a game to check out if you like tactical games that require some thought.

All versions of The Sentinel on The King of Grabs:
BBC Micro (the original), Amiga, Atari ST, PC MS-DOS, Commodore 64, Amstrad CPC and ZX Spectrum

More: The Sentinel on Wikipedia