Anyone who has played a Zynga game (Farmville, MafiaWars, Cityville) is familiar with their ubiquitous energy model - it's present in a huge swath of Facebook games, even those not created by Zynga. Here's a brief explanation of the concept, for those still untouched by energy's dark sheen:
Energy, in brief
Players start with 10 energy, represented by a yellow bark + lightning bolt icon. Each click in the game costs you 1 energy, and provides you with some benefits (coins, experience, food, etc). Every 5 minutes you gain 1 energy, if you are currently below your maximum.
When you gain a level, your maximum energy is increased by one (this often stops at some point - maxing out your energy at 25 or 30 or 50, depending upon the game) and when you gain a level your energy is immediately refilled. This is critical at the beginning of the game, and matters very little later on, as we'll see.
So when a player starts a new Zynga experience they are carefully led through a series of early clicks, earning experience/whatever each time. Just as they run out of energy they earn enough experience to advance to level 2 and whoosh! Energy is refilled. Then they keep going and once again just before their 11 energy is up whoosh! They gain another level. This usually lasts 3 or 4 levels - giving players a good 45 clicks or so before they are actually unable to play further. This is why refilling energy at each new level is so critical - because it turns the start of the game into an extended tutorial - which would be impossible otherwise.
After this initial introduction, players are encouraged to log back in every couple hours (when their energy is refreshed) and perform more tasks. A series of quests pushes players further and further in the game experience - directing them sternly but compellingly towards a habit-forming relationship with the game.
Why is it necessary to limit player's ability to play the game at all? Why not simply let players click as much as they like, as opposed to holding them back? The answers are revealed in the mechanical design of Zynga's games, and are simultaneously more and less evil than you might originally suspect.
Games, like all activities, require some amount of investment from players. Sometimes we talk about economy within a game, but it is just as valid to talk about the economy created by playing the game instead of doing something else. Arcades required travel time, monetary investment, and a rather high degree of skill. In exchange for that you got some social interaction (hopefully positive) and the game experience itself. In order to put more time into playing, you had to increase your skill or pay more money.
As players moved away from arcades, we found a new economic equilibrium. Player death was mostly eliminated as a limiting factor thanks to QuickSave and Checkpoints - so games became exercises in time. How many hours did you put against the game? How many achievements did you grind out? How many sidequests did you finish? Asking for lots of player-time justified escalating game prices - up to $60 at the peak. (I actually remember paying $80 retail at Toys-R-Us for Mega Man 3, but let's just pretend that things like $100-dollar Neo-Geo cartridges never happened.)
The problem with requiring time from players was that it required huge amounts of content on the development side. This was an accepted spiral for about a decade - charge more for your game, provide more content of higher quality, require more time investment, change more for your game. This cycle started to fray around 2004, and broke completely around 2009. This style of thinking will always be around (like people playing original Quake) but it's no longer the primary delivery method for games.
The ending of the console-dominated game era (consoles still exist, but they no longer dominate. At all.) means that games have become shorter, less demanding of time + attention. Casual is a term I'm not entirely comfortable with, but it's a fair stab at the direction the game form is heading. There are more games, and games require less focus, less mindshare. Finding a game isn't hard anymore - finding a game you like isn't even terribly difficult. So if games are so easy to play and easy to find, what draws people in? How do you get a bigger-than-average player base?
The answer, in one form or another, is scarcity. People will try to gather something precious. If your game is played for real money, like poker, you've got a huge playerbase ready. If people find your game competitive & worthy of dedication, like Street Fighter, Starcraft, or Halo, you've got a different sort of playerbase. Zynga decided that they would make the game itself - the ability to play - the scarce resource. This is a bit novel - it's not something that would occur to console developers or arcade owners. Preventing people from playing the game doesn't sound like a good strategy.
But, as it turns out, it can work. It works because the actions are trivial, and the rewards great. Playing a Zynga game gives a thrill like printing your own money - it just pours out in great gushes, so long as you have energy to fuel it.
But there is another side which works in tandem to scarcity - alternative economies. Because players can, in fact, buy more energy by spending real money on the game. This works on two levels:
1- The majority of players (who don't spend money) equate their actions as being worth some amount of real money. If I can buy 10 energy for $1, then playing my 10 energy I got this hour was like saving $1 of my money, right? When I decided to sign back in, I might think to myself I can earn another $1 by signing in to play once more before bed.
2 - Players who do spend money on extra energy have powers beyond regular players. In many cases far beyond the powers of regular players. It's like becoming the best Street Fighter champion ever by just putting in 50 cents instead of 25. The ability to buy power is a strong allure for some players.
But here's where it all goes Wrong
Zynga's Energy System is a powerful compulsion engine, and it's a tolerable solution for a small handful of Facebook games. But Zynga (and other developers) have slathered Energy bars across almost every Facebook game playable today, and it's killing us. Energy in Farmville works, because farmers can only get so much accomplished in one day. Budgeting your time between actions is exactly what all adults have to do every day. But for every Farmville you have 25 Adventure Worlds, where Energy acts like a vice grip on any enjoyment players might be able to find in the core mechanics.
Let's look at Adventure World, which I loved for about 20 minutes.
In Adventure World, you are clearing debris / overgrowth from mazes of ruins in search of treasures. Initially you can only deal 1 damage per click, but as you earn money you get better equipment, and can clear bigger brushes faster. That's awesome. What's not awesome is the fact that it takes about 60-70 clicks to clear a map, and you only have ~20 energy. (I'm simplifying here - it actually takes 150 energy to clear, but you get a return of about 1.3 energy per energy spent... just like slot machines!) So you only get to tackle part of a level, and then you have to sign out, wait an hour or two, and then come back to it.
In this case I don't feel like I'm allocating my energy - I'm not making strategic decision about how to best spend it - I'm just prevented from playing the damn game. Time stops when I leave the game, and it picks up when I come back in.
It's clear that nobody at Zynga thought carefully about this and decided that the energy model was a good fit for this game. Rather, Zynga just throws their standard mix of tools into every game they create - which makes them all sort of blur together in my mind. It's as if a red car won some important race, and then everyone painted their car red to, in hopes that it would make them move faster. This is bad enough within Zynga, but dozens of other developers are applying the same "like Zynga" methods across all sorts of games as well.
Perhaps a better metaphor is the way so many older games get re-imagined as a FPS - even when that overtly breaks the premise of the original game.
I want to like Zynga (if only because Brian Reynolds is there) but I feel more often than not that they don't understand their own strengths. They're like Sony during the PS2 era - on top of the world and totally unaware that they've lost sight of what to do next.