A paragraph from Donald A. Norman's The Design of Everyday Things:

For many everyday tasks, goals and intentions are not well specified: they are opportunistic rather than planned. Opportunistic actions are those in which the behavior takes advantage of the circumstances. Rather than engage in extensive planning and analysis, the person goes about the day's activities and performs the intended actions if the relevant opportunity arises. Thus, we may not go out of our way to go to a shop, or to the library, or to ask a question of a friend. Rather, we go through the day's activities, and if we find ourselves at the shop, near the library, or encountering the friend, then we allow the opportunity to trigger the relevant activity. Otherwise, the task remains undone. Only in the case of crucial tasks do we make special efforts to ensure that they get done. Opportunistic actions are less precise and certain than specified goals and intentions, but they result in less mental effort, less inconvenience, and perhaps most interest.

Opportunistic play, with all the qualities suggested by Norman, can be a lens through which to view and design certain game systems. It is a design lens, or methodology, in the same vein as Clint Hocking's notion of improvisational play. The improvisational play in Far Cry 2 is constrained to the firefight, however, and does not easily scale up.

The mission structure and unfolding narrative is highly intentional; map icons provide the player with a guaranteed mission type and location. Opportunistic play is not limited in the same way. Opportunity can be found in the securing of a safehouse the player happens to find themselves near, to shooting an explosive barrel that unexpectedly crosses the player's gunsights.

Hocking says "randomness and unpredictability are where improvisation is born," but it is only through opportunistic actions, when "behavior takes advantage of the circumstances," that improvisation is allowed to take place.

In designing a set-piece or firefight for improvisational play it is necessary to recognize the explosive barrels, mounted machine guns, enemy patrol paths, places of cover, etc. as opportunities for the player to take advantage of in the course of their improvisation. Consider the difference between the mounted machine gun in a Far Cry 2 outpost and the mounted machine guns found in Uncharted 2.

In Far Cry 2, a dozen factors such as player location, health, ammo supply, enemy location, etc. may align to turn the machine gun into an opportunity to take advantage of. Uncharted 2 takes the mounted machine gun and makes it a crucial task. After you've fought your way up to and neutralized the machine gun, you can be sure a wave of enemies will appear within its arc of fire. It's not an opportunistic action in service of improvisation, but the next stop in a highly authored and scripted scenario.

One other example of a successful use of opportunistic play in Far Cry 2 is the blinking diamond briefcase indicator in vehicles. Searching for briefcases could have been an entirely intentional activity, requiring the player to set aside a large amount of time and effort, but the blinking light provides an opportunity for discovery in the normal course of play. The exact same opportunity mechanic exists in Fable 2's dog.

It's important to note that an opportunity that is inconvenient is no opportunity at all. The worst recent offender of this is probably Grand Theft Auto IV. From time to time Nico's girlfriend or buddy calls with a mission opportunity that requires they first be picked up. Unless the player is within a few blocks of the character's location, it becomes inconvenient to drop everything and accept the mission. What should be an opportunity is actually just a mission alternative that, if followed, requires all the effort and planning of a crucial task.

If the designers had recognized the characteristics of effective opportunistic play they could have easily made it so calls were only triggered when the player is near the NPC, or simply spawned them a block or two away from the player's current location. These tasks also suffered from their banality--playing pool with a virtual friend is hardly enticing enough to make one cancel their current plans and drive for 10 minutes in the opposite direction.

There is a relationship between how exciting an opportunity is and how far out of the way the player is willing to go to take advantage of it. Fallout 3 is extremely effective at encouraging distraction and throwing the player off a set path.

Most people have probably had a Fallout 3 experience similar to the following anecdote: I was walking towards a map marker for an active mission I was invested in when I spotted in the distance what I would later discover was Tenpenny Tower. This huge tower sticking out of a flattened wasteland was so fascinating that I immediately changed my course towards it.

Several minutes later I found myself drawn to a large factory previously hidden behind a hill, and fully explored that before continuing towards the tower. My original mission was long forgotten, as opportunistic play had let me carve out my own path through the narrative based on my personal interests and curiousity.

If we agree with Norman that opportunistic actions can generate the most interest in people, then designers should make an effort to provide opportunities, not crucial tasks, whenever possible. In RPGs, an opportunity to save a family from bandits becomes a crucial task when it is not stumbled upon but formalized with a quest-giving NPC or an unavoidable random encounter.

Games like Baldur's Gate and Fallout 3 have numerous examples of opportunistic actions--opportunities that presented themselves as the player explores the wilderness. Dragon Age: Origins and Fable 2, in contrast, make many of these same types of events crucial tasks by only activating them with direct permission from the player. Almost every action is planned, with an explicit goal written out in the Quest Journal.

When this is the case, it does not matter if the quest is optional or part of the main story, the event is "precise and certain" in the quest journal and therefore less interesting than something stumbled upon. Running out to find and kill the bandits you've been told are terrorizing the family is less dramatic than coming across an unexpected bandit attack in progress.

We play games because the cliché is true: It's the journey that matters, not the destination. A destination is simply a specified goal, i.e. a crucial task. Games that are made up of a series of opportunities will always provide the player with a more powerful and personal experience than those that consist solely of destinations.