Hardly anyone plays a game as it’s written. Sometimes that’s because the game is poorly written and nobody can work out quite how a rule is supposed to work. Sometimes it’s because the GM hasn’t read the book properly and has to wing it. There are plenty of other reasons why you might want to tinker around with the rules of a game as well.
God of the Gaps
No game system is perfect and no game system can completely cover every possible situation that a character might find themselves in. Looser games can be a bit more adaptable to this while, perhaps, older and more complex systems have a much more rigid structure that’s harder to adapt. If you find your game straying into territory that isn’t covered (at least by the books you have) then you’re going to need to come up with something to fill the gap.When you’re trying to fill a gap in a game your best bet is to derive the new system from something that already exists in the system. If the game has rules for climbing, but not balancing, you can adapt the climbing rules into something for keeping your footing. If the game doesn’t have rules for attacking a helpless enemy but does have rogue rules for backstab attacks, you can adapt those to allow other characters to use them in special circumstances.
Only if you can’t derive a new rule from the existing rules should you consider coming up with something whole cloth as otherwise you’ll begin to break down the system integrity and come up with all sorts of special exceptions, which gets complicated pretty damn quickly!
The Thrill of the New
Sometimes you just want to add something to the game that it doesn’t have. Perhaps you’ve played a new game with some neato character class, style of magic or other innovation that you want to bring in. Perhaps you want to drag some alien race from a new film into your existing game system. New options, new armour, new weapons, new spells, even new skills. Most of these things can be modelled on existing game elements and systems and they should, generally, be comparable to what already exists in the game in terms of power. In SF games you can march technology and innovation on a bit further, provided technology of all kinds keeps up, fantasy games you might want to rein things in a bit or leave the really big trouble for plot devices – which are allowed to break the rules anyway.
No Sir, I don’t Like it
Sometimes games just have some aspect that you can’t wrap your head around or that you really don’t like. The way initiative works, how much damage it takes to kill someone, how hard it is to hit, how hard it is to aim. These are generally some of the easiest things to fix – you can generally just adjust some values – but the knock-on effects can be hard to predict. Changing hit points or damage in D&D, for example, can throw certain powers and encounter difficulties off-kilter with far reaching effects. It may take a lot of back and forth to work out what works best for you and your group and when you get into a convention or tournament scenario you’re not going to able to play according to how you prefer anyway.Fundamental Changes
Sometimes you want to make fundamental changes to the game, like affecting how the whole rolling system works. The most far reaching of these is in influencing the base dice rolling mechanic of the game. Most games fall into one of three categories:
- Single Dice – Games that roll a single dice to resolve chance have an equal chance of getting any result. This tends to result in wild swings of fortune and (relatively) disempowers modifiers. D&D, for example, uses a d20 to resolve checks and a great deal is down to chance.
- Multiple Dice – Games that roll multiple dice to resolve chance tend to cluster around the average result and more extreme success or failure is much less likely. Games that use this are much more influenced by modifiers – such as skill – and chance and luck play a far lessened role. SLA Industries, for example, uses 2d10 and results tend to cluster around ’11’.
- Dice Pool – Dice pools roll multiple dice against a target and accumulate successes from the number of dice that score over that number. Dice pools tend to fall somewhere between the two, averages results are common but manipulating the difficulties, number of dice etc allow all sorts of modifications, the size of the pool is all, which does tend to emphasise modifiers that increase or decrease that.
Changing from a single to a multiple die system wreaks an enormous change on the feel of a system, multiple dice tend to result in a grittier game while single dice allow for more heroism, betting everything on a good roll and dramatic reversals of fortune. A fairly common change in d20 systems is to replace a single d20 with 2d10 (or even 3d6). In so doing it’s probably best to remove the need to ‘confirm’ critical hits as extreme rolls (2 or 20) are much less likely. Equally, changing things the other way instantly alters a game in the opposite direction, allowing for far wilder results. If you wanted to make SLA much more high-octane and chancy, you could change it to a d20 system from its 2d10 rolls.
Sometimes you want to take something that you think rocks from one system and bring it into another system. Perhaps you want to change the way that damage works or import an initiative system that you like (I’ve done that with the initiative system from Blue Planet many a time). With the various elements you like you can, theoretically, mash together a game that has all the features you love from all the games you’ve ever played. This is extremely difficult as games can be very different and none of these elements will work together particularly well without a lot of modification. All things considered, you’re better taking these things as inspiration and writing your own system whole cloth if you’re going to take things that far.
Balance Can Suck My Balls
A big concern for a lot of games seems to be keeping things fair and balanced between the various classes, powers and circumstances. Boring! Balance doesn’t have to mean homogeneity. Different strengths and weaknesses in different arenas are balanced. This isn’t to say you shouldn’t be careful about introducing new elements and rules just keep in mind that it’s always easier to add something to a game than it is to take it away. It’s down to the GM to balance things with encounters and problems and suitable enemies, to give all kinds of characters a chance at the spotlight and at being useful, not so much down to the rules themselves. Otherwise everything can tend to end up bland and samey.