Usability in game design (Portal)

Nick Dymond - September 7th, 2009

I’ll admit to being a little behind the curve on this one, but last weekend I finally got around to playing Portal, the 3D action-puzzler from Valve Studios. Much has already been written about the game, but what I’d like to briefly discuss is the work that went into usability during the game design process. In this respect, as with many others, Portal is a master-class.

Valve have a culture of play-testing from week one of production, something that has obviously had a large impact on the success of their games ( The developers’ primary challenge was to introduce the new gameplay element of portals’ – doorways that can be opened up by the player using a portal gun’, a device that allows the player to fire two portals. The antagonist can then walk through one portal and out of the other. Simple, right? Wrong. The system opens up a whole world of perceptual confusion in novice players, who find it difficult to comprehend the rules of the new physics they are manipulating. One common mistake is to believe that you are switching between dimensions, rather than remaining essentially in the same locale. To counter these issues, Valve introduce game elements gradually, allowing the player a level of independence and experimentation, whilst guiding them subtly towards a greater understanding of the game. Obviously this hand-holding approach is common in game design, but I can’t think of any other instances where it is so transparent and effortless. It never once patronises the player.

The visual design, although completely immersive, is relatively spartan, reflecting the research facility scenario and more importantly creating a strong, consistent aesthetic to the puzzles encountered. One good example of their ethos is that all interactive elements in the game world are circular or rounded, whereas non-interactive elements have squared edges. There are many more complex aspects to the design work, but unfortunately I have work I ought to be doing…

If you’re interested, there is a developers’ commentary ( in the game that is as revealing as it is enlightening. I would certainly suggest playing through it first before taking a look at the commentary. See how many mistakes you’d have made were it not for the exhaustiveness of Valve’s design methodology.

P.S. Oh, I almost forgot (thanks for the reminder Jess): there’s a 2D flash version that gives you some idea of how the game works

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