The d2 System is a role-playing system that can be used with nearly any kind of dice, from coins to standard six-sided dice to d20s, as long as it has an even number of sides. I am using it as the basis of Exalted Lite, Forgotten Dawn, and Solar Storms.
Because it only uses a d2, I will be referring to 'flipping coins' where most other systems will involve rolling dice. When rolling dice, the easiest thing to do is consider an even number a success ('heads'), and an odd number a failure ('tails'). Feel free to use another means if it suits your group.
This isn't a normal generic system, since it cannot be used in a standalone fashion. For examples, see Forgotten Dawn, Exalted Lite, and Solar Storms. Each uses these rules as their core, but expands upon them by defining their own attributes, and the subsequent rules from them.
The core of making a test in d2 is to flip your attribute in coins, counting heads as 1 (a success) and tails as 0 (a failure).
And that's it. When using dice, you can either count odds as failures and evens as successes, or count the lower half of results as 0 (1-3 on a d6, 1-5 on a d10...) and the upper half as 1 (4-6 on a d6, 6-10 on a d10). In OpenRPG, roll [(Attribute)d2-(Attribute)] to get the appropriate result. I will also be providing a roller with a modified 'd1' that generates 0's and 1's accordingly.
For game masters who wish it, if a test generates no successes when the difficulty was greater than half the player's pool (difficulty 2 on 3 coins, 5 on 8, etc), the test can botch, resulting in mess happenning.
Most of the d2 Systems rules have to remain pretty basic, due to the level of customization needed. There are a few common themes which follow identical or similar guidelines, however.
A feature of the d2 System is the ability to scale, where a group of two or more coins can be counted in a single coin. This mostly comes into play in settings like Solar Storms, where the vast difference between capabilities needs representation.
Scales are assigned a letter, from A to Z. Human scale is considered to be scale B. Each scale is considered to be ten times as good as the scale previous. For example, a score of 10 on scale C would be only be a score of 1 scale D, but a score of 100 on scale B, and 1,000 on scale A.
Attributes in the d2 System are a part of the customization of the system. While they should be comprehensive, they should also be a short list:
|Exalted Lite||Forgotten Dawn||Solar Storms|