This is very easy straight sytem.
You have a number in different attributes and skills from 1 to x.
When making a check you either roll your attribute or skill (depending on what skills or attributes apply) with D12.
That's with a Strenght of 3 you roll 3 D12. One of the rolled D12 has to beat the target difficulty given by the GM (between 2 and 12).
If you roll multiples of one number, then you add +1 to this number for each copy of that number you rolled.
As example: You roll 4d12 - 3, 8, 8 and 11. Since you rolled 2 dice showing an 8, they are combined to make a 10 (2+8). If you rolled 3 dice and got 10 on all three dice, you'd have 13 (10+3).
The difference between the target difficulty and your rolled number is the measure of success or failure.
When you make contested rolls, the difference between the rolled numbers is the measure of success or failure.
It's pretty simple rule system and makes critical failures and successes very rare.