Review by Colin Phipps

The Parallel Dimension v1.8 is a complete replacement for the Shores of Hell episode. The episode comes with a good (but of course completely ignorable) plot; you have been selected to teleport into a parallel dimension, trigger a device which will destroy all its evil inhabitants, and then escape. Needless to say, the plan goes wrong, and you have to fight your way through the entire dimension to complete your mission.

The episode requires the Boom engine to play. Partly this is because of VPOs, but also a number of new effects are used; there is deep water, and new graphics are imported and used with translucency to created coloured glass windows.

Also, a dehacked patch is used to extensively modify the behaviour of some of the decorations. All of the gory decorations and monster corpse decorations are modified so that they are shootable; this means that you can blow away some of those frustrating obstacles, but also that they sometimes get in the way at inconvenient moments.

I found that the early levels in the episode were a bit disappointing; there is little evidence of Boom features, adequate but not impressive architecture, and quite a few dead-end traps. But later on the episode is excellent, in particular E2M6 & E2M7 are great maps. Here are my thoughts on each level:

1. The Beginning of the End - A trivially small level, comparable in difficulty to MAP01 of Doom 2. I've had this debate with people before, about whether the first level of an episode should be small and easy or not; while I usually think it should be small, it should definitely not be this easy. There is some interesting architecture through, very much in the Doom 1 style.
2. Guardian of the Gate - Another small level. The main area is a single courtyard, with a central building and a high balcony around the outside. It's a fast fight, as you run around avoiding imp shots, but this is the only interesting fight at the level. There is far too much ammo, and an inescapable acid pit to jump. The architecture is pretty basic, though the exit (you get into a vehicle to go down a tunnel) is a good idea.
3. C.O.D. - This level starts with you beside your overturned transport from the previous level, which appears to have been shot by a tank. You are just outside of a compact base which forms the entire level; you have to fight some odd buildings outside and teleport into the base proper. The level is a strange mix of styles, with wood, marble, and cement textures all within a few seconds walk of each other. There are also a lot of frustrating inescapable acid pits in one of the major link rooms. While the architecture is a bizarre mixture, there are plenty of good fights and traps scattered through the level, only slightly marred by what I consider to be an overuse of troopers, which just get in the way and slow down the fights.

4. The Hidden Bunker - A very Shores-of-Hell style level this one. You are inside some kind of base, with a large courtyard with an acid lake in the middle. This area is a complicated fight, which forces the player to live dangerously for several minutes. The level makes good use in places of new Boom features, like coloured glass, and conveyor belts.

   However, I got a bit frustrated while playing this one. There are quite a few acid areas, which have to be passed multiple times, but you are given only a single rad-suit. Further confusion is added because some acid hurts, but some doesn't. Also, one acid tunnel starts with a rad-suit, but you immediately turn a corner and discover that there is a key door; you should have saved that suit for later.

5. Gate Control System - This level reminded me in many ways of the Military Base (Doom 1 E1M9). The level centres on the starting courtyard, with lots of areas branching off which have to be explorer to find keycards. There are even some of those imps on extremely tall pillars out of a lake. The architecture is fairly sparse, but there are some good features, particularly some good Boom features.

   The level has few really difficult fights, with mostly basic opposition, but these are still interesting due to the clever traps and monster placement. There is a clever fight at the start, a good example of how a few well placed minor monsters can cause a lot of damage. There is a good secret for a supercharge too.

6. The Biological Laboratory - This is a great level; the architecture captures the best of the Doom 1 style, with some excellent Boom features added in for good measure. There are lots of windows and such which allow you to see areas long before you reach them; the level all fits together in a very satisfying way.

   There are some excellent fights too: there are several places where the player is forced to fight monsters at close range with little or no space to retreat. These are often mixed with enemies firing from a long distance at the same time, which makes the fighting even more complicated. There are also quite a few good secrets.

7. Mineral Mines - The episode now plunges underground, into a complicated mesh of mining tunnels and storage areas, and lava tunnels. I thought the tunnels with railway tracks, the large storage caverns piled with crates, and the other features like fork-lift trucks and water pumping systems, created the most convincing mine level for Doom that I have yet played (though the railway lines should have been smoother). The fights are nothing special in themselves, but coupled with the great atmosphere of this level it was great fun to play.
8. Apocalypse - This level starts with a large base, with a very impressive control room at the centre of it - I particularly liked the futuristic computer displays. The plot of the episode comes back here, as you trigger the destruction of the parallel dimension, and have to escape the base past piles of fried enemies. You teleport back from the parallel dimension to face the final showdown, with a huge number of monsters which escaped with you; it's the usual thing, cyberdemon and hordes of helpers, but there is very little health, so it becomes a war of attrition as you hope to have enough left to face down the cyber. It's a good final challenge.

The music is changed for the entire episode, using a mixture of Doom 1 & 2 musics.

Overall, this is a good episode backed up by a good plot. The early levels are disappointing, but it is worth playing on, because the several of the later levels are excellent. The original Doom style is nicely recaptured, and enhanced by some good fights and Boom features.

The episode does support co-operative play, but it sucks. Don't, is the simple advice here, because the first trap immediately cuts off all but the first player; at later levels there are lots of acid areas with limited acid suits that will make co-op impossible, not to mention the extra cyberdemons added for multiplayer.