Pick Up That Can

The final quadrant of our graph is represented by Half Life 2, a game renowned for being one of the first to introduce general physics objects as a core mechanic in a mainstream shooter. There is stuff all over the place in Half Life 2, and almost all of it can be picked up and manipulated with the iconic Gravity Gun. In fact, many of the game's puzzles involve using the various physics objects to solve simple lever or weight problems (and this has been increasingly true in the episodes.) As a result, Half Life 2 is both cluttered and interactive.

The problem of consistency

Now that we've broken down our examples, it's very interesting to note that the two games at the top of our interactive axis do almost nothing to indicate to the player what can or can't be manipulated. The Gravity Gun in Half Life 2 does have a subtle animation that activates when an object can be picked up, but this is pretty much the extent of their signaling mechanism. There's no indication at all if you're just picking stuff up with your hands.

Both of the games at the static end of our graph, on the other hand, do attempt to indicate when objects are interactive. Mirror's Edge applies the same red highlight treatment that they use to suggest efficient climbing routes, while Uncharted 2 has two different approaches depending on the item in question. For things that are meant to be picked up – which are primarily guns and grenades – they play a flashing effect on the item itself. For environmental objects such as statues or carts that can be pushed the game generates a HUD prompt when the player is sufficiently close to the object to initiate interaction.

Why would games that have less interactive objects feel the need to highlight them? The answer is actually fairly obvious: because these objects are the exception rather than the rule, it's necessary to counteract the player's expectation that items in the environment are there primarily for aesthetic reasons. In essence, these games need to momentarily break the immersion they've crafted in order to make certain that the player understands what needs to be done.

The problem of fidelity

It's worth going back to the concept of immersion as it applies to interactive objects. Games like Uncharted 2 fill their environments with interesting props precisely because it makes the world feel more alive, more lived in. This is despite the fact that these objects typically don't do anything, but that's because they don't really need to. From a development standpoint, it's much easier (not to mention more efficient) to make great looking stuff to fill out the world when you don't have to find a use for all of them or spend valuable CPU time handling their physics.

Furthermore, the high quality of the environment and the desire for seamless immersion creates pressure to make the objects that are interactive blend in as well as possible. This is, of course, exactly the opposite of what's easiest from a game design perspective, and it isn't a new problem. Back in the days of yore, adventure games found themselves in a similarly difficult situation. As hardware improved, background art got increasingly lavish and detailed and, as a result, it became important for interactive items to meld well with these more immersive scenes. One of the side effects of this progression can be found in the phrase "pixel hunt," a derogatory term that came to be associated with many later adventure games.

Because the worlds were so detailed, filtering objects that were important to the game from the ones that were important for reasons of aesthetics became a matter of hunting around the scene looking for spots that would give you a "use" cursor. This was not a particularly fun mechanic, and the problem contributed to the eventual decline of the genre. More modern takes on adventure games offer various aids to reduce the issue, with many offering player abilities that cause all interactive items to flash or highlight briefly.