## Flipping Coins: Dice for a Desert Island

If you’re like me, you’ve had those times when you’re at your Grandfather’s for Xmas, and your younger cousin who’s really curious about this whole “roleplaying thing” wants you to run a game for her, but you try to weasel out of it by saying you don’t have any dice, and of course she’s like well why’s that important and doesn’t understand why you won’t run something, until finally you accept your filial duty and run a pickup game hunkered in a corner of an upstairs hallway where the rest of the relatives won’t notice, but eventually they hear the weird cawing noises you make when the intrepid wizard and her sneaky companion creep through the crow-infested orchards outside the ruined castle on the way to find the lost crown of their forgotten kingdom.

It could happen to you. It could happen to anyone: you want to game, but you have no dice.

What do you do? Flip a coin, or maybe a bunch.

Any range of numbers you could roll can be easily represented with a bunch of coins. The more coins you use, the more fine-grained the result.

It’s easy: divide the size of your die by the number of coins you are going to flip. Flip your coins, and multiply the number of heads you get by the result to find your roll. Zero heads equals the lowest value (a 1 usually).

Let’s take the ubiquitous d20. If we use only two coins we divide 20 by 2 and get 10 for each coin, so if we get 1 head we get a 10, 2 heads is a 20, zero heads is a 1. A better spread is probably 4 coins (20/4 = 5), which gives us 1/5/10/15/20 for zero through four heads respectively. We could also go all the way up to 10 coins, whatever.

Want to do an odd range like 10-60 for that big fireball? Just treat the number range the same as a single die of that size. We’ll fudge and call that 0-50 + 10. On two coins that’s 10/35/60 (0/25/50 + 10). Or flip five coins and have each head do 10 more damage.

Are the odds the same for flipping coins as rolling a die? Nope, not exactly. Without getting too technical, the more coins you flip the more of a bell curve you create, so the mid-range results will be more likely.

Interestingly if you use 4 coins to recreate a d20, you have a 1 in 16 chance of either a 1 or a 20, which is pretty close to the normal odds. So feel free to let someone get a critical if they flip four heads, or hit them with a house rule fumble if they get all tails.

Now go forth and teach your relatives how to game. You have one less excuse.

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Dagoth Grundzsays:Castle Falkenstein used decks of cards too, and was a very sexy book to boot!

Andy Shortsays:Actually, playing cards make a brilliant substitute for dice, and if you work out an appropriate system, you can actually use court cards, jokers and the suits etc to provide extra information. The numbered cards alone give you D10 values, or you can ascribe values to the suits to act as a D4. Draw a joker and call it a critical.

A new RPG system coming out soon called No Dice (at http://www.nodicerpg.com if you’re interested) does this really well; suits are used to represent aspects of your character’s stats, act as indicators for bonuses and penalties when drawing skill checks, and can be used to show different fighting styles in combat. Draw a card, and if you’re on suit for that kind of attack you get a bonus, get the wrong suit and you suffer a penalty. Court cards can be used to trigger special attacks (draw your assigned court card on-suit for the ultimate critical!). The GM can even use the suits to get extra information about his NPC’s reactions to you.

Also, dominoes.

ben robbinssays:That’s very cool Mak.

Maksays:For a while when my son was 8 and 9 we RPGed a lot while in the car, driving to lessons, to visit relatives, etc. Good way to pass time. Since we often didn’t have dice on hand, I used a couple of different methods of generating pseudo-random numbers.

One of the simplest ones we used was the digital clock on the dash, which my son couldn’t see from his seat in the back. Even or odd? Simple 50% probability. Of course you can’t make more than one such check in close succession; fortunately, kids don’t tend to be great at estimating the passage of time. To mix things up, sometimes I used the “scan” feature on the radio, with the volume turned down. As long as there’s more than three or four radio stations, you’ll end up with a series of “random” numbers. You can “scan” twice or three times, backwards or forwards to mix up the order in which the numbers will appear.

A more systematic method I discovered on the ‘net somewhere; the author recommended it for RPGing while hiking. It requires the use of a digital watch. You set the chronometer running, and after waiting a breath or two, you stop it and check the hundreds of a second. Basically, you’re rolling percentile dice. A great way to play with children who understand the basics of probability and percentages. Drawback is you have to take your eyes off the road briefly to look at your watchface.

A deck of cards also does the trick if you’re visiting at Grandma’s house. By discarding face cards, you can easily simulate a d10 roll; discard 7s to 10s and you have d6s. Leave a joker or two in to simulate a wild die or critical successes or failures!

As far as game systems go for that situation, the basic form of RISUS could work well.

Stevesays:I used Shadows while baby-sitting my 5 and 7 year old daughters after church (my wife had a meeting). I didn’t have a d6 and we just used a coin to determine whether my daughter or her shadow got what she wanted. I recommend it as a fun, easy start-up game for camping, travel, or baby-sitting.

Gerald Cameronsays:May I suggest Shadows for times like this?

It’s a page of rules, uses dice, but common d6s are fine, and it is intended for play with younger children, but is adaptable to any age group (even adults, I would argue).

I haven’t played it yet, but it seems tailor made to the situation in question.

Stephensays:My friend and I did this one time back on a boy scout camp out with a checkers piece. Neither of us really analyzed the numbers or the probabilistic similarities to real dice (we were in like 5th grade), but we did a basic pass-fail flip followed by a confirmation flip to see by how much one passed or failed. It was crude, but my friend ad-libbed a whole adventure that way. We usually remembered our dice after that, but I’ll keep your post in mind if I ever end up doing this again.

Asmorsays:1: What self-respecting geek doesn’t have his dice handy at all times? I usually keep my dice in my messenger bag that I take to school and elsewhere.

2: I hate my relatives. :)

3: Nonetheless, cool idea.