The IBM PC port supports VGA graphics, with an additional lighting effect: objects and terrain become darker the further away they are from the point of view.

In The Sentinel, the player takes the role of a Synthoid (called just "robot" in the US version), a telepathic robot who has to take control of a number of surreal, checkered landscapes of hills and valleys, by climbing from the lowest spot, where the hunt begins, to the highest platform, over which the Sentinel looms.

Sometimes (depending on the individual skill of the player), it is necessary to replay a level in order to beat it with less energy than the last time, since the difficulty is not incremental.

[5] It received a Gold Medal award by Zzap!64 magazine,[6] describing it as an exceptional piece of software in a class of its own, and refusing to give it a numbered rating as a result.

The ZX Spectrum version received a CRASH Smash award,[7] the magazine praising its originality, atmosphere and tension.

[11] A preview of a nonexistent sequel called Monolith appeared in 1995 in Italian magazine The Games Machine as an April Fool's Day prank.

In December 2020,[14] a freeware game named Monolith, based on that hoax, actually came out[15] and was reviewed in issue 1/86 of Zzap!

[18][19][20][21][22] Annwn: The Otherworld[23] (2019) has similar gameplay with a Celtic motif and several changes to user interface and level structure.