Gnosys Fantasy Roleplaying System

From the introduction:

Okay, here's where we will talk about the basic rules.

The main rolls used in this system are called "challenge rolls" or CR from now on. A CR is %dice + modifier against opponent %dice + modifier, where the higher of the two succeed. i.e.: I attack with my sword(my action is 30%), and my foe blocks with his shield(his action is 10% + 10% for the shield = 20% action), I roll %dice (I roll a 45%) add the modifier(45 + 30 = 75%), compare it to his roll(he rolls 50% + 20%modifier, so 70%), mine is higher so I succeed, and he does not block the blow. This is done for most actions, even non combat action, i.e. moving quietly against opponents hearing, climbing a wall against the hazardousness of the wall.

There are two different %'s used, first is the skill %(S%), this is the actual skill you have in this skill. next is the action %(A%), this is the modifier used when making a CR.