Sources: Orson Scott Card's Ender's Game, Suzanne Collins' The Hunger Games, J. K. Rowling's Harry Potter series, Yu-Gi-Oh, Star Trek
Why We Love 'em
Games are an enticing blend of action and strategy, competition and team work, skill and luck. As kids we'd go outside to play Hide-and-Seek, Tag, and Dodgeball, then come inside and play Checkers, Monopoly, and Uno. Games take many forms. In the real world, they have physical limitation: space and technology, money and friends. In speculative fiction, the only limitation is your imagination. Everything is off the table--including moral compunctions--and the stakes are incredibly high. Are you ready to play the game of your life?
It's hard to just pop out an original idea for a game. If you have one, great. If not, you can begin with a simple game and embellishing with new rules, new equipment, and new player combinations. Or you can smush two games together. Hide-and-seek Checkers. Uno Tag. Once something strikes your imagination, develop it further by considering these aspects of gameplay:
All games are based on competition. Someone has to win and someone has to lose. The objective tells the player how to win.
Usually, it's pretty simple. In The Hunger Games, which drops adolescents into an arena and has them fight to the death, the last one alive wins. In Ender's Game, where children play a strategic version of laser tag in null-gravity, the objective is to "kill" or "disable" your opponents while keeping a requisite number of your own team "alive." Sometimes the objective varies slightly depending on the player. In Hide-and-Seek, the hider's objective is to reach home without getting tagged, whereas the seeker must tag the hider before he gets home.
The situation becomes more complicated when you add rules. Rules determine how the player must play the game--what they can or cannot do in order to keep the game fair and fun. Rules are tiresome. They bog down the story with exposition and limit the resourcefulness of the players. Keep them to the absolute minimum.
What if, however, your game does have a complex amount of rules? In high school, I used to watch an anime called Yu-Gi-Oh which was based on a card game so complex, I had to actually get a deck of cards and read the rules before I understood it. But I enjoyed the show. In a case like this, do not, do NOT sit down and explain the rules to the audience. Shove the player into the game and explain the rules as it becomes necessary. This, by the way, is the same way most people explain a new game to their friends--by making them play it.
However, if you want to include the official rules in the appendices for clarification, I'm sure the audience wouldn't mind.
What's the biggest obstacle to victory in a game? Nine times out of ten, it's the other players. This is where the author has fun, drawing up the different personalities of the competitors. But before we get to that, let's have a look at how they face up against each other.
Is it a team game or individual? Can there be one winner or many? How many people can play at a single time and how does this affect the play? Is it a tournament, where people fight against each other one-on-one, until the two champions collide? Is it a free-for-all Battle Royale? Do players start off in teams and eventually compete as individuals? Do they start as individuals and form teams? Do teams get reshuffled? Do you boot off members of your own tribe?
All these things facilitate the character's relationships. It goes without saying, if you want drama, place friends and loved ones on opposite sides with your hero, and have your hero have to work with enemies and rivals.
Generally, your hero's opponents should have some leg-up on him. Some, if not all of them, need to be bigger, stronger, smarter, more experienced, better-connected, tougher, richer, or more ruthless. If your hero waltzes in with an advantage--if they are considered the best of the best--do something to knock them down a notch. In Ender's Game, Ender is the most brilliant boy in battle school, so the teachers manipulate the game to make it more difficult for him.
Field of Play and Equipment
Here's where the imagination really comes into play.
In a normal game, you're limited to whatever 2-D space is available: a schoolyard, a cul-de-sac. But in speculative fiction, you can utilize air space, if you want, and build whatever terrain you desire: jungles, volcanos, ice plains, the ocean. Still, before you go crazy, consider what role you want the field to have. Is it meant to be a neutral place for the players to wage war upon each other? In that case, keep it simple--a flat smooth field, a court, the airspace over a farm. But if on the other hand the field is meant to be an obstacle in and of itself, go crazy. One arena mentioned in Catching Fire, (the second book of The Hunger Games Trilogy) contained beautiful flowers, glistening fruit, and vibrant butterflies--all of which were extremely poisonous.
Think, too, about how long you want the game to go on. As a general rule, the game lasts for a few hours, a simple enclosed field is best. If you want it to go on for days, you'll need a larger space with shelter and access to food and water. Think of a baseball field versus the island on Survivor. Be aware of the physical boundaries of the game. What keeps people in the zone of play? Are there penalties for stepping out of bounds?
The next thing to consider is equipment. In real life, you can play several games with simple equipment (like a ball) or no equipment at all. But screw real life, this is fantasy and what good is fantasy if you can't have massive flame throwers and laser-shooting dinosaurs every now and then? In Yu-Gi-Oh, they bust out larger-than-life holograms just to make a card game more exciting. Equipment is also where money becomes an advantage. If someone can afford a T-Rex with a ray gun and all you've got is a Deinonychus with a paintball gun, the odds aren't exactly fair, are they?
Purpose and Stakes
Why are people playing this game to begin with? With most games, the answer is "for fun," with maybe the additional benefit of getting exercise, practicing a skill, spending time with friends, or proving something about oneself. Quidditch functions like this. But if your game is a little more dangerous, sinister, or downright psychotic--if you wonder why anyone in their right mind would play this game--then you need to dig deeper to find the game's purpose.
A little history of the game--who founded it and why--can be helpful. But the game may have evolved since then. It's more useful to look at who currently maintains the game and why. When in doubt, follow the money. In The Hunger Games, the Capitol hosts the games, provides the equipment, and pays the prize. They maintain the game because, to them, it's a tool display their complete power over the districts and prevent them from rebelling.
But the government isn't the only ones putting in money. A sizable amount of citizens spend money to give additional equipment to their favorite competitors. Ordinary Capitol citizens put in money because they've grown emotionally attached to contestants or have bets riding on them. It's all entertainment to them. Poorer district citizens sacrifice their small savings on the slim hope that their children survive. And here's the thing to remember: a game may have different purposes to different people. What's frivolous entertainment to some, may be life-and-death to others, may be cold manipulation to someone else.
Stakes are similar to purpose, but it deals more concretely with the costs and rewards of winning and losing the game. Sometimes, you pay an entrance fee to play and sometimes you gain a huge prize for winning. But money is the most common and least interesting of the stakes. What has more value is a person's sense of dignity, his principles, his loved ones, a people he represent, a life long dream.
A game is about risk. There's always something to gain and always something to lose. On a petty side, it might be money, pride, or reputation. In more extreme situations, the hero's life may be on the line or the lives of his people. In Ender's Game, humanity itself was at stake. Of course, the more dangerous and stressful the game, the more it costs our hero just to participate. He may face injury; he may start slowly losing his mind.
People play games in certain ways. It's not necessarily stated in the rules--it's just the convention. People in the past have used certain strategies to win; others copy them. Over time, it's just assumed that there is a "right" way to play.
Here's where your protagonist can gain a slight advantage. Presumably, you've stacked the deck against him. He's outnumbered, outgunned--maybe he's never even played the game before and has no idea what he's doing. But all that can turn into an advantage, if he invents a novel approach--something that defies the convention, something that his opponents have no idea how to fight against.
By the way, it's not just your hero who can defy convention. If the committee in charge of the game decides on a rule change, the whole game can get shaken up. In this case, everyone might be clawing for a new strategy, with very interesting results.
You know what happens when you give people rules? They go out of their way to break them. In a game, this is called cheating.
And you know what? Cheating is actually pretty fun. Bad guys do it all the time, with classic maneuvers such as modified equipment, bribing/ pressuring important officials, or downright sabotage. But did you know good guys can cheat too?
Two caveats, though.
...The Game is Evil
If the game demands human sacrifice or supports an oppressive regime, your hero can cheat any which way he feels like and the audience will cheer. Cheat big, cheat little, cheat subtle, cheat obvious. Whatever he needs to do to destroy the game itself.
...The Game is Rigged
Not just a little rigged. There is no possible way for the hero to win. The classic scenario is the Kobayashi Maru in Star Trek--a simulation of a defeat that Kirk wins by re-writing the program. This kind of cheating favors the clever and the prepared.
...The Stakes are Impossibly High
In this case, the game might be fair and reasonable, but factors outside the game has put so much pressure on the hero, he desperately needs to win. Think dying mothers and loved ones held hostage. Expect this kind of cheating to occur at the last minute. Initially, the hero tries to play fair, but when some disaster convinces him he cannot win on his own, that's when the temptation to cheat becomes too much.
Depending on how evil his opponents are, the audience might forgive the hero for roughing them up a little. But the hero cannot physically hurt opponents who are neutral or nice.
Well, he tries not to. The nature of cheating is that, by not abiding by the rules, you leave room for others to get hurt. The hero's scheme might get out of hand and accidentally injure or even kill someone. In that case, expect lots of guilt and regret.
...With Bonus Points if He Protects Others.
The hero doesn't always cheat for himself. Sometimes, it's his teammate or even his rival he's concerned for. Said person might not appreciate it, but the audience usually appreciates his unselfish intentions.