Here I will write up some mechanics that could be used for this game.
Real 3D
You have a character value from 1 to 20.
You have a difficulty (or another character value) from 1 to 20.
You roll three 6-sided dice.
If the sum of the 3 dice are equal or lower than your character value, you handle it safely. Wich means, you don't loose the control.
If the sum of the 3 dice are higher than your character value, you mess up and loose control. This will have consequences depending on the gap between the roll and your character value.
Add the highest die to your character value. If the highest die is 6, you can add the second highest, too. If you rolled two 6s, you can add all the three dice to your character value.
If the sum is higher than the difficulty, that's a success, you managed to take the obstacle. The wider the gap between the sum and the difficulty, the better the success is.
If the sum is equal or lower than the difficulty, you didn't succeed. The bigger the gap between the sum and the difficulty, the bigger the failure becomes.
This core mechanic intends to simulate the two faces of skilledness.
On one hand, you can use a skill to safely control what you do. (For example drive/fly a vehicle without crashing it.) This incorporates some very easy difficulties, too. (Like passing through an easy obstacle course.)
On the other hand you get sometimes lucky and even you yourself are staggered how have you been able to manage the task and you will be sure that it won't happen again. (Like passing through an obstacle course you thought impossible.)
Note, that you can pass the obstacle AND crash the vehicle. If you roll too high, you went too far. You made too big circle to evade an obstacle and lost the optimal track by doing so.
Conscious decisions can be made by adding or substracting modifiers before the roll is made. If you are a daredevil, you add to it, if you are a safe softy, you substract from it. Both can prove as futile after the roll. There are only two objective values that you know how they behave: your skill value and the difficulty.
If 2 characters are rolling against each other, the accomplishment is how big success they get. If either of them rolls above his/her character value, (s)he made a mistake that can be exploited.
Idea for close combat (not a realistic one, only to try the mechanic): The two players decide secretley how aggressively their characters will fight (a whole number). The two characters roll simultaneously. The aggressivity modifies the value of the highest die rolled. (More dice are only added up if rolled a natural 6.) The damage made by your character is the gap between your sum (your value + highest di(c)e according to the rules) and the character value of your opponent. Damage made by your character is only delivered if your opponent rolled (the 3d6) above his/her character value.
Possible problems:
This mechanic has the problem that it uses a "roll below skill value" with dice having a bell curve. The bell curve is good for making performance mostly mean, but rolling under skill value only means that the bell curve rescales the array of possible values. The same result could be achieved by using 1d20 and the buying of higher values would be exponential expensive.
Luckily there is this little rule about the possibility for the player to modify the result of the roll. This rule would have no meaning if the result of the rolling would give an even result: but by having the bell curve the player can estimate the result of the roll and can realistically decide what modifier (s)he really needs.
Real examples for Real 3D
Running. The higher difficulty you achieve (having an open ended roll like in Shadowrun) the quicker you run. If you roll above your "run" value, you become such exhausted that you can't do anything right after. The exhaustedness is defined by the gap between your roll and your "run" value.
I still haven't decided whether sprintin and long distance running should be separated or is the latter just sprinting with a high negative modifier. You always roll under, but you won't get very quick. I would rather use the latter, because it would be better for a game intended to be realistic to have more generic rules. For sprinting and for long distance running the physics and the biology is the same. Only the tactic changes wich is exactly the modifier for.
Physical Danger. People act differently when they are in physical danger. It can be practiced and learned to physically defend yourself, wich means it is a skill. Let's call it physical awareness. If you are running from a hitman, you will run quite differently as when running at the olympics. If physical danger is imminent, this skill has to be used. It is mostly used together with another physical skill. By succeeding in this skill you can evade or lessen physical harm even if you didn't manage it by using your other skill.
Self Inflicted Difficulty
This is just a basic idea wich can be used in any RPG that has some difficulty value. There are situations where the players can define the difficulty directly. For example take Han Solo flying through the asteroids to shake off TIEs. He is raising the difficulty of flying to give the Imperial pilots a hard job, because they have to struggle against the same difficulty.
The GM determines based upon the terrain what is the range of difficulties that can be chosen (how deep you go into the asteroid field) and the same difficulty is applied to the chasers, too. This can work in D20, in Shadowrun, anywhere if there is something like a difficulty or target value.
Note: It doesn't work every time a contested check would work, it only works when there are two enemies: the difficulty of the task and the opponent with the same problems as yourself.
Using Skills Together
This can be tried to in any RPG that uses skill or attribute checks. If the act needs more than one value, even then roll just once and compare it to more values, as you would've rolled for each and every check the same result. This means that you can't excel in a lesser skill if you didn't in a better one. You can't add up the results (you can't add nor if checking against a difficulty, nor the gap of success), but you can differentiate more discrete outcomes.
In this case for example you can use the skill "run" and the skill "physical awareness" together if you are running from someone chasing you, if you think that the pursuer wants to harm you.
First you make up a modifier for the roll for the running and for the physical awareness seperately. You roll once with the three dice and compare them to the skill value "run" as stated above in the example. Then you compare the result of the same roll to your "physical awareness" value. The gap you rolled under the skill is added to the success of the running. If the pursuer caught you, you can decrease the probability of a hit and the damage caused by the success of physical awareness. If you rolled above your physical awareness, you can only decrease the damage inflicted, but not the probability of a hit.
If you run and someone is attacking you it's a totally different issue. You don't run because of fleeing from physical harm, you have to roll seperately for the two seperate skills.
Base Values
Now, listen to this. I was thinking about this over and over and still don't know how bad impact would this have on the mechanic. But I think it would make it more fun, would implement the attributes and I think it can even be useful for some balance problems of the mechanic Real 3D. (If you have a skill value of 5, it won't help that the difficulty is 5, too. You simply can't roll under 5, the probability is very small.)
The skill values range from around 1 through 20. (These are the normal values with 3-18 the meaningful ones.) Let's have basic attributes ranging from 1 through 6. Each and every skill has 1 to 3 basic attributes attached to it with an importance value. The importance values of the basic attributes attached to the same skill add up 3.
Example:
- Running (strength 1D, dexterity 2D)
- Weight Lifting (strength 3D)
I wrote a letter D after the importance value to make it more intuitive, because AFTER you rolled the dice you assign all the three dice to the basic attributes attached to the skill. You assign as many dice to the attribute as the importance.
Example:
- When running you roll the dice and they come up: 3,4,4. You decide to assign a 4 to strength and a 3 and a 4 to dexterity.
Then you compare the result to the attribute wich you assigned to and you use the difference as a modifier. If you rolled under the attribute it will make easier to roll under the skill value and it will raise the success. If you rolled above the attribute it will make harder to roll under the skill value and it will lessen the success.
Example:
- Your run skill has the value of 10.
- Your strenth is 4, your dexterity is 5.
- You assign a 4 to strength and a 3 and a 4 to dexterity.
- You get a -3 modifier when comparing the roll (11) to the skill (10) wich means it saved you from tripping.
- You get a +3 modifier for calculating the success, wich means it will be 10 (skill) + 4 (highest value) + 3 (attribute modifier) = 17 instead of 14.
Looking into it:
I decided to assign the dice to attributes after rolling, because it would else just escalate the result: if you roll low, it will be lower, if you roll high, it will be higher. But in this case you can optimize wich can be imagined as the insticts working.
I don't know if it is correct to use such an abstract method (assigning AFTER) in a game intended to be realistic. It would only be correct if each and every mechanic would come from the need of realism. This time the cause was not only realism, the only realism in this mechanic is that it implements attributes, but there are other priorities here, too, wich seem much more important: it's elegant (you don't have to roll seperate dice for attributes, and it's the third use for the same result) and it's easy (you don't have to add much, you mostly have to compare).
Now I'm really curious what you think about this one.
An important note: When generating the character and advencing it, the value of basic attributes are based on the skill advancement and not vice versa! The character gets strong because of weight liftin and not chooses weight liftin because he had a strength of 18 already as a teenager. Yes, there is "build" and "talent", but those values are something else and not the brute, unmodified strength wich tells you only how big you lift.
Specific Use of Base Values
If we accept that the base values like strength, eye-hand-coordination, etc. have specific purposes, than the complexity of Real 3D with Base Values can be explained.
You still use the Real 3D rule and you still tie dice to base values, but not only for a modifier, but to have specific uses.
For example you are fighting wich uses eye-hand-coordination for hit, strength to do damage, balance to evade hitting. You roll 3 dice and you compare it to your "skill" value. You get an avarage rating how this turn will look like for you.
Then if you want to have higher damage then indicated by the result, you tie a high die to your strength.