Sentinel Returns
Developer(s)	Hookstone
Publisher(s)	Psygnosis
Composer(s)	John Carpenter
Platform(s)	Windows, PlayStation
Release	1998
Genre(s)	Puzzle
Mode(s)	Single-player, multiplayer

Sentinel Returns is a video game developed by Hookstone, produced by No-Name Games and published by Sony (under the Psygnosis label) in 1998, for PC and PlayStation. It is the sequel to The Sentinel by Geoff Crammond and features 651 levels, a multiplayer mode and a soundtrack (titled "Earth/Air") composed by John Carpenter and arranged by Gary McKill.

The PC version has native support limited to a software display mode and an accelerated Glide mode, because in 1998, 3DFX cards were the de facto standard for gaming 3D graphics. However, modern computers can run the game in accelerated mode with the wrappers nGlide,^[1] dgVoodoo,^[2] OpenGlide^[3] or zeckensack's Glide wrapper,^[4] which translate Glide calls respectively into Direct3D or OpenGL calls.

This game looks very different from its predecessor. While in The Sentinel the levels were bright and colorful, in Sentinel Returns they are dark and gloomy, with flashes of light being emitted when an object is created or absorbed, and the mouse pointer dynamically lighting the world. The game has a general "hallucinated" look: the skies are made out of contrasting streaks of color; the trees look like sperms; the boulders breathe and have a sphincter on the top; the sentinels and sentries are hybrids of flesh and metal; the sentinel stands are covered with skin and have four vertebral columns protruding from the corners; the "specimen" representing the living part of the synthoid resembles a hydatidiform mole, and it squirms and lets out a shriek when injected with a needle.

Controlling Synthoids that are standing at a higher level is fundamental to the game, because only the objects which occupy a visible square can be interacted with (the player may absorb or create objects on a boulder if the sides can be seen). While doing so, the player must watch for the rotation of the Sentinel and be careful not to stand in an area which the Sentinel can see, or else it will start absorbing energy from the Synthoid, and when the energy is gone, the game is over.

Height is gained by placing a boulder on any visible square, and putting a Synthoid on the boulder. The player may then transfer consciousness to the new Synthoid, and absorb the old one. Stacks of boulders of any height may be created, if the player has enough energy. In order to absorb the Sentinel, the player must create a stack of boulders of sufficient height that the Synthoid on top can look down on the Sentinel's platform. When the Sentinel has been absorbed, the player may no longer absorb any energy from the landscape, although objects may be created as normal.

In later levels, the Sentinel is assisted by a number of Sentries. They behave exactly like the Sentinel, but absorbing them is not necessary to complete the level. Unlike the Sentinel, the Sentries do not stand on a platform but on ordinary squares. Attention must also be paid to nearby trees: if the Sentinel or Sentry cannot see the square the Synthoid is standing on, but its head is visible and there are trees in the vicinity, it may transform one of them into a Meanie, which will force the Synthoid to hyperspace and lose 3 units of energy. If the Meanie itself cannot see the player's square after a full rotation, it will turn back into a tree and the Sentinel or Sentry will resume rotation.

The rotation of the Sentinel and the Sentries is slow and predictable. However, if there are many Sentries, there will be few safe locations anywhere on the landscape. If either the Sentinel or the Sentries come across a source of energy (boulders or a synthoid), their rotation stops while they absorb the energy, one unit at a time. Meanwhile, to keep the total energy of the landscape constant, a tree is created randomly on the landscape for each absorbed unit of energy.

List of objects that can exist in the Sentinel world:

• Tree (1 unit of energy)
• Meanie (1 unit of energy)
• Boulder (2 units of energy)
• Synthoid (3 units of energy)
• Sentry (3 units of energy)
• Sentinel (4 units of energy)

A level is won by absorbing the Sentinel off its platform, creating a new Synthoid in the place of the Sentinel, transferring the consciousness to it and hyperspacing to a new level.

The number of levels that are skipped between two that are played depends on the amount of energy the player has accumulated when he jumps into hyperspace: absorbing less than 50% of the total energy present in a level will skip a level; absorbing between 50% and 69% will skip two; absorbing between 70% to 89% will skip three; absorbing between 90% and 100% will skip four.

• The action is faster and the movements (rotating the synthoid and transferring the consciousness from a synthoid to another) happen in real time. This allows the player to move much more quickly across the landscape and to complete a level in far less time. To counterbalance this, the Sentinels and Sentries (which have a FOV of 28 degrees) are able to absorb energy from the synthoid at a much greater rate.
• By absorbing a sentry, a tree is created in a random square in the level.
• There are "only" 651 single player levels, while there were 10,000 in the first episode. For this reason, it is only possible to skip up to 4 levels when one is finished. In particular, the player will skip: 4 levels by absorbing from 90% to 100% of the energy in the level; 3 by absorbing from 70% to 89% of energy in the level; 2 by absorbing from 50% to 69% of energy in the level; 1 by absorbing less than 50% of energy in the level.
• A multiplayer mode is present. To start a multiplayer match on the PC version, the host needs to set up the random creation of a level, choose a DirectPlay service provider, type a host name and a player name, and finally select "Host a Session". Every guest needs to select the same service provider and select "Join a Session". The goal of multiplayer mode is to race each other to the Sentinel; every player can teleport each other's synthoid to lower levels. The supported DirectPlay service providers are IPX, TCP/IP, modem and serial.
• The game has two endings. To see the first one, the player must beat the 651st level. To see the second one, the player must beat every level, or "achieve 100% orchid", as this is expressed in the game.

Although their gameplay is almost identical, the two versions have several differences in their graphical look.

• The level selection and level loading screens are fully polygonal in the PC version, while they are made out of 2D elements in the PS1 version.
• The 3D models have more polygons in the PC version than in the PS1 version.
• The PC version has colored lights (although only with the hardware accelerated rendering), the PS1 version does not.
• The levels have different architectures in the two versions.
• The checkerboard patterns are more evident in the PS1 version, which has also rougher-looking slopes than the PC version.
• The skies have orbiting planets in the PS1 version, they do not in the PC version.
• When an object is created in the PC version, it appears abruptly. In the PS1 version, a seed (when a tree is created) or 2/3 "energy clusters" (when a boulder or a synthoid is created) fly to the selected square, while rotating polygons assemble into the object.
• When an object is absorbed in the PC version, it disappears abruptly and generates a number of "energy rings" which quickly disappear. In the PS1 version, it disassembles into rotating polygons, while a seed (when a tree is absorbed) or 2/3 "energy clusters" (when a boulder, a synthoid or a sentry is absorbed) fly to the player's POV.
• The explosion of the sentinel is seen from the player's POV in the PC version and as a non-interactive scene in the PS1 version.
• After a level has been beaten in the PC version, a vortex made of a spiral and a number of triangles appears above the sentinel stand; in the PS1 version it does not, but is mentioned anyway in the manual.
• In the level-ending hyperspace scene, in the PC version the POV looks up into the vortex, while it looks down toward the synthoid in the PS1 version.

Next Generation reviewed the PlayStation version of the game, rating it two stars out of five, and stated that "Those who have fond memories of the original or who crave a new PlayStation experience should rent before buying. It's definitely an acquired taste."^[5]

• Sentinel Returns at MobyGames
• Sentinel Returns at 3DGamers