If you've talked to me recently, you know I'm quite enamoured with the Battlestar Galactica boardgame. If you haven't played it, you really should. It's one of the best games I've ever played, digital or cardboard. It's a game about paranoia, suspicion and betrayal, which are disappointingly rare experiences as far as games are concerned. It evokes those feelings with both excellence and ease. And perhaps most importantly, it does so exclusively through the game's mechanics.
I've never seen the Battlestar Galactica show (I know, I know, I'm planning to watch it as soon as my wife and I finish Rome), so the feelings the game evokes are not due to the game's fiction. Although by all accounts, the game does replicate the feeling of the show quite well. But the BSG fiction is just a supporting element and a way to tie the game into something people are already familiar with. The feelings the game evokes are entirely due to its design.
I'm going to try to break down specific mechanics that help the game foster the atmosphere that it does. For those that haven't played, this likely won't make much sense. But hey, that's just another reason to go play the game. As I thought about this, one commonality is how much depth many of the mechanics have. Even once the mechanic is understood, clever players can find unexpected ways to utilize it and, especially if they're a Cylon, find ways to manipulate the perceptions of other players. So without further ado:
Anonymity and Randomness in Crisis Skill Checks: Cards played in skill checks are played face down, and two random cards (of a finite deck of two of each kind) are added (unless a special card is used to force them all to be played face up). Unless there are three negative cards, the humans cannot assume the skill check has been sabotaged by a Cylon.
If there are more than three negative cards played, which players can draw those colours comes under scrutiny. If all the negative cards are green and yellow, suspicion is going to fall on the Political characters. Of course, there are ways to get colours your character cannot draw. So the behaviour of characters for the past few turns comes under scrutiny. Has someone been playing a lot of Consolidate Power cards, getting two cards of any colour? What were those colours? Has someone been spending a lot of time in the Press Room, drawing yellow cards? A clever Cylon might have encouraged someone to hit up the Press Room, just to then spike a skill check with yellow cards and try to cast suspicion on them. In short, the anonymity and randomness in the skill checks end up not only allowing for higher order thinking, but suspicion is almost always the outcome if they go wrong.
Character Access to Skill Cards: The types of cards characters have access to creates interesting depth in how they can affect skill challenges. In some ways, Pilot characters (and Giaus Baltar) have the easiest time of sabotaging skill checks. With access to three or four types of skill cards, it's more difficult to pin them down as playing against a skill check. But with limited access to leadership and politics cards, it's difficult for pilots to participate in the shipboard skill checks of sending someone to or freeing them from the brig, and changing the presidency. Also they won't ever start the game as president or admiral.
Voting: Since it's difficult for any one person to accomplish a skill check, many skill checks (especially those involving the Brig or the presidency) end up seeming very much like votes. Whether a character participates or abstains can potentially shed insight into their true nature. This has the secondary effect of potentially creating alliances between players. If I helped keep you out of the Brig, you're probably at least a little more likely to trust me. Similarly, moving the Presidency from one character to another (rather than to yourself) has essentially created one ally and one enemy.
As a Cylon player, the ideal situation is to keep the humans factionalized. By allowing for "voting" in the skill checks, not only are player's motives called into question (creating suspicion), but alliances can potentially be formed. Should those alliances then be betrayed, and it's very much in the Cylon player's interest to do so, the feeling of being mislead is inevitably heightened.
Players being forced to make decisions: Certain Crisis cards give the option to either attempt a skill challenge and risk a very negative outcome, or simply choose a slightly less awful outcome without any chance of success. Other cards simple force the current player, the admiral or the president to choose between two unpleasant options. By forcing players to make a decision with real severe consequences, it creates stressful moments where that player's judgement is called into question. It provides the opportunity for a Cylon player to make the obviously worse decision if it's really damaging to the humans.
But most importantly, it plants the seed of doubt in other players' minds. If you're suspicious of someone, you don't want them to have an opportunity to do grievous harm. Putting them in the Brig means they'll not draw Crisis cards and they'd lose the Admiral title. But putting someone in the Brig unnecessarily can do major harm to the humans' chances of success, so it's not a decision to be made lightly.
Positions of Power: Beyond the decisions they're forced to make in the above circumstances, the Admiral and President also have two very important roles. The President has access to the Quorum cards, which afford a number of powerful abilities, including sending someone to or free them from the Brig without needing a skill check. The Admiral decides where the Galactica goes when it jumps, which can greatly help or hinder the humans. These roles are not balanced with respect to the other player's abilities.
This means it's very important to make sure the Admiral and President are trustworthy. I can tell you first hand that if one person is both the Admiral and the President and they turn out to be a Cylon, the humans are in a bad way. The Admiral and President end up heavily scrutinized, but the humans have to be very careful about changing those roles, lest they change it from a human player to a Cylon.
Cylon Reveal Abilities: Should a Cylon reveal themselves and not be in the Brig, they get to deal extra harm to the humans players. This encourages the Cylons to play subtly until they can position themselves for a devastating reveal. Engaging in a scorched earth policy from the outset will get that Cylon dropped in the Brig. As damaging as the Cylon can be, it's distrust and suspicion amongst the humans that will do the most damage. A good Cylon will foster that distrust, ideally sowing as much dissent as they can without revealing themselves. And only then should they pull the ultimate reveal. Without the advantage of reveal while outside of the Brig, Cylons would be less penalized by openly sabotaging the humans' efforts.
Imperfect Information: Fundamentally, Battlestar Galactica is a game of imperfect information. Whenever the Admiral looks at the destination cards, he isn't allowed to share their contents. If he selects something harsh, it's up to the other players to believe when he says the other thing was worse. Players can occasionally look at another player's loyalty cards, but again that information is for their eyes alone. When they claim that person is a Cylon (or not), the other players can act on that information or not depending on how trustworthy they feel that player is. The only time any perfect information is ever allowed is when a Cylon reveals themselves. Otherwise, it's just trust. And having to rely that much of trust means suspicion is an inevitable consequence.
This is by no means thorough. But it does reveal some trends (build mechanics that result in suspicion, making trusting other players dangerous) that fosters the atmosphere of paranoia and tension that makes BSG such a novel experience. I really encourage anyone who hasn't played it to find a way to do so. Given how well established certain experiences in games are (as excellently as they may be implemented) the feeling of a good game of BSG is really quite novel. Plus, it's hard to offer higher praise than saying it's almost guaranteed to make you hate your friends, in the best of ways.