Interaction Density

August 19, 2016

In computer adventure games, interaction density is a term used to refer to the relative level of hotspots in a game that the player can manipulate in some way. These manipulations may be necessary to progressing in the game or they may just provide clues, humourous interchanges, or background details about the characters and game world. Basically, it refers to how much “stuff” can be done in a given location in a game.

The Golden Age

During the late 1980s and early 1990s – the Golden Age of point-n-click adventure games, where Sierra and LucasArts ruled the roost – interaction density tended to be fairly high. In part this was due to the interfaces of the day. It was common for games of the era to offer multiple “verbs” that could be used to interact with the game environment in different ways.

[Sierra's action bar from Space Quest I.]
Sierra's action bar from Space Quest I.

[LucasArts's verb grid from Indiana Jones and the Fate of Atlantis.]
LucasArt's verb grid from Indiana Jones and the Fate of Atlantis.

Sierra games used an icon based system that typically provided anywhere from four to seven basic actions that could be performed on a hotspot. LucasArts offered nine to twelve. On top of these basic actions, both Sierra and LcuasArts games allowed players to accumulate an inventory of objects. The objects could then also be used on hotspots in the game world (or on each other) to do even more special case interactions. With such an array of options, even having just two or three hotspots on a screen could mean having dozens of potential interactions. Granted, many of those interactions resulted in generic “that doesn’t work” type responses, but that wasn’t important. What was important was that a player could try those interactions. It made the game worlds feel bigger and more responsive. It didn’t matter if you’d never actually try a given combination, just knowing you that could if you really wanted to was the important thing.

Games of that era also had interesting real world physical limits that helped to increase the interaction density in a game. This was back in a time when even if a game had a CD based release there would almost always be a floppy disk based release as well. When you’re trying to fit a game onto a handful of floppy disks, there’s only so much content you can include. Having rooms in a game that had few or no hotspots was a luxury that most games couldn’t really afford at that time. So most rooms in those games had at least a few hotspots on which this wide array of interactive options could be applied.

The Dark Age

Move forward a few years to the decline (some even say death) of adventure games, from the late 1990s through the early 2000s. During this time, many point-n-click games streamlined their interfaces down to two basic actions: examine and interact. The type of interaction would be assumed based on the object a player interacted with. For example, clicking a door would cause it to be opened if it was closed or closed if it was open. Although this got rid of a lot of those generic “that doesn’t work” responses, it also got rid of some of the openness that a player instinctively felt a game environment has.

At the same time, many point-n-click adventure games also changed their art styles. Gone were the lush hand painted and scanned backgrounds of the Golden Age. In their place, intricate pre-rendered 3D scenes with real time rendered 3D characters laid on top emerged. This happened at a time when the resolution for games was increasing from the Golden Age standard of 320x200 pixels to 640x480, 800x600, or, in some rare cases, even higher.

Two things happened with this shift in visual presentation that impacted interaction density. First, with the increased resolution it became possible to include finer and finer detail in a scene. For example, a dinner table might now be able to actually show detailed cutlery where previously only a couple of smudgy pixels could be used to imply the same. This led to games having a lot of areas that looked like they could be interacted with, but actually couldn’t.

[One of many empty, winding path rooms in Awe Games' Agatha Christie adaptation of Evil Under the Sun.]
One of many empty, winding path rooms in Awe Games’ Agatha Christie adaptation of Evil Under the Sun.

Second, when you create a painted background, you have that one scene to include a game. However, when you create a 3D model of a location, you can place the virtual camera in many different areas and render many different background screens of those areas viewed from different angles. Combining this ability with the increased disk space afforded by CD and later by DVD meant that many games expanded the size of their game worlds by including rooms that were largely empty of things to interact with.

The end result with this generation of games was that while you had many games that were highly detailed and beautiful to look at, the playing experience was very empty. You could go for long stretches moving between empty scenes while encountering areas that looked like they should be hotspots but weren’t really. Consequently, although the overall amount of interaction in a game might be roughly the same as before, the perceived relative interaction density went way, way down. Adventure games of this era tend to feel more empty and more limited because it feels like there’s less that can be done.


I’ve been reflecting on interaction density in games a fair bit in the past two weeks due to my own upcoming Sleuthhounds Halloween adventure game. Adventure games are presently experiencing a renaissance of sorts, with new developers trying new things with them, especially indie developers. One interesting feature of this new crop of point-n-click adventure games is that they do tend to be smaller as far as room counts go, in many cases even smaller than the games of the golden age.

While these games – and Sleuthhounds is no exception – have maintained the more limited two action interface, the interaction density feels higher. The compactness of these games, in terms of screen count, has collected more hotspots within individual screens than previously. The (mostly) empty screens of the Dark Age games have fallen away and game worlds are feeling more alive again as a result.

One step I’ve taken in my own games to increase the interaction density is to try to replace those generic “that doesn’t work” type responses of the Golden Age games with responses tailored to the interaction you’re trying (which is not always easy when you’re trying to combine chattering vampire teeth with a fortune teller’s tent). As my games to date are fairly compact, the number of interactive hotspots in an entire game is small enough that I can at a minimum write and record custom lines for each interaction. Some such superfluous interactions even get their own animations simply because I’ve been building up a good store of such animations and can apply them to some of these “that doesn’t work” situations.

As a fan of the genre, I’m hoping adventure games continue their resurgence. I’m hoping too that such games will continue the trend to being “tighter,” to have fewer locations within them but make those locations more meaningful by making them more interactive. Like a good book, when playing a game sometimes you just want to lose yourself in another world. That can only happen with the depth that comes from high interaction density.