Excerpts from The System chapter:
P'tor-ra uses a two-sided system, depending on the species involved, but several of the basic mechanics are identical.
Each creature has 4 basic statistics - Strength (STR), Mind (MIN), Dexterity (DEX), Agility (AGL) - each valued with a die value from d4 to d10. For every statistic, the human norm is d6. No die value may exceed d10 and if any statistic drops below d4, that individual has died. A fifth statistic, Complexity (COM), is used for Mental tests on tools.
Anything beyond simple actions (and, for saurians, even many simple actions) require making a test by rolling one or more dice and adding any appropriate modifiers. All tests are opposed by another statistic, either of the individual targeted or a die assigned by the game master.
Test rolls may be modified by many conditions. Tool bonuses and condition effects are the most common and simplest to implement. These represent the advantages or disadvantages given to an individual based on equipment possessed by them or by the environment and position between him and his target.