The games that made Portal 2

Ready for another tour around the glorious world of Aperture Science? With good cause! But no game is ever built in a vacuum. Here's a look at some of the games that directly and indirectly gave us one of the greatest sleeper hits in gaming history, and the most exciting sequel of 2011.

Prey

No, not the one that finally came out in 2006. We're thinking of the original Prey, which was originally due to take the world by storm around 1998. The whole game was sold based on its ability to fold space, make buildings bigger on the inside than the outside, blow holes in reality, and more. In practice... it never came out. The Prey we finally got is almost entirely unrelated, bar the presence of portals.

However, despite this, Prey was a very important game. Its portals directly inspired other developers to play around with the concept, and it wasn't long before we started seeing them show up. Epic for instance put portals into the original Unreal, and while they were much more simplistic than Prey's interpretation (most notably, they had to be static), any level designer could now play with TARDIS style buildings and space warping. In practice, it didn't really happen, but at least the idea was out there, ready to take centre stage barely... well... a decade later, as seen by the fact that it was a whole other Prey that first really showed them off in a commercial game. It did reasonably well, but then Portal appeared in 2007, and made the whole concept its own. Here's a glimpse of what could have been:

And here's Unreal doing the cut-down, static version, not long afterwards:

System Shock

Let's see. Sci-fi setting. Psychotic female AI. A main character trapped in a world run by a computer tormentor... it's hard not to draw certain parallels between the two games. However, the most direct one isn't necessarily SHODAN herself, cybernetic god-empress of Citadel Station though she is, but the way she exercised her power. System Shock pioneered a new kind of narrative, one where your enemy was a constant presence in the game through audio responses and very minor amounts of scripting. She constantly phoned up with cheery messages like "Welcome to my death machine, interloper!" or "If you go into that room, I will kill you...", along with a healthy amount of monologuing and increasingly empty threats as you worked through every level, methodically foiling her five billion different plans for world domination. Even on the ropes, she manages to remain scary - especially in System Shock 2.

As with portals themselves, Portal wasn't the first game to use the same trick, but it was one of the most successful. The irony of an actual AI character having precisely no AI on her side shouldn't be ignored, but nor should the effectiveness of just a handful of memorable voice clips played at exactly the right time. This applies both to when you're doing things right - solving a test chamber for instance - and when you screw up. In Portal, one of the best examples is if you get trapped, and GLaDOS demonstrates her fake-perception and environmental control to let you out again. In System Shock... let's just say that at one point there's a lever that nukes the Earth. If you pull it, SHODAN is Quite Pleased.

(As a related note, calling GLaDOS a rip-off of SHODAN would be a mistake. She may or may not have been a direct influence, though rogue AI is nothing new in science fiction, but she wasn't the driving force. Initially, GLaDOS was a very small part of Portal, restricted to only a few short appearances. Even that is largely credited to writer Erik Wolpaw having discovered the comedy of lines delivered by text-to-speech while working on Portal. The question of which of the two AIs would win in a fight has yet to be answered, though there are are pictures and there is 'sexy' fan-fiction . Be very, very afraid.)

Here's a Let's Play of System Shock 1. Prepare for REALLY BIG PIXELS.

Narbacular Drop

This isn't simply a game that inspired Portal, but Portal's direct predecessor. It was a student project, and to be honest, not much of a game. The concept is identical to Portal, with a main character (Princess No-Knees, since she can't jump) running around a fantasy world and laying down demon-shaped doors on any natural surface. As with Portal, the puzzles primarily come from how much of the world you can't slap them onto, with metal in particular quickly becoming your nemesis.

The basic idea is strong, though the feel isn't particularly good - especially after playing Portal proper, which refined the concept to be smoother than silk - and this version of the game is far, far too short to be particularly satisfying. That didn't matter. Valve snapped the team up almost immediately and set it to work. Those concepts, in a new futuristic setting and brought to life by GLaDOS, struck a chord like no other. It's difficult to remember now that Portal was originally just the 'other' game in the Orange Box - the throwaway little puzzler next to the mighty Half-Life: Episode 2 and Team Fortress 2.

Download Narbacular Drop here. Alternatively, here's the whole game:

Tag

Tag is the Narbacular Drop of Portal 2 - the game that gave it one of its most important mechanics. Even at a quick glance, it's clear the two games were born for each other. Like Portal, Tag's levels are all very simple, largely monochrome worlds built entirely around a single gun-based mechanic. Instead of throwing portals however, you spray paint from a Super Soaker type device. Each colour has a different effect: green makes you jump, red makes you go fast, and blue lets you stick to surfaces, up to and including walking on ceilings. The puzzles are built around the interplay of these elements, typically squirting a track of red paint with a glob of green at the end to propel you across great distances, or squirting green down two platforms to wall-jump to the top. One of the best things about the game is that while there isn't much scope for inventive solutions and thinking outside the box in this version - it being little more than a short proof of concept - you never have to worry about running out of paint. As long as you've picked up the colour's can, you get as much of it to play with as you want.

Portal 2 copies almost all of these mechanics, with the exception that you use portals to spray the paint around instead of having a dedicated gun to do it, and there are more environmental hazards and intricacies to the world than the occasional moving train or nasty fall. As with Narbacular Drop, this isn't idea-thievery - Valve hired the team to come work on Portal 2. To see the basic idea, download the original project here . As for what they've been doing since, we'll be seeing that... ooh... real soon now.

Tick. Tick. Tick...