Mechanics:

Attacking: Your d20 roll+Related Weapon Attribute+Related Weapon Skill. So let's say you firing a Pistol. You roll a 12. So, you add your Agility Attribute (For this example, is 3.), and your Projectiles Skill( For the example, 5.) So 12+3(Agility)+5(Projectiles)=20. And to resolve Combat, whoever has the highest roll wins. Attacker wins, the defender takes full damage. Defender wins, they still take damage, but it is halved.

Defending: Same as rolling for attacks.

Armor: Unlike D&D, Armor doesn't allow you to dodge attacks. In Insanity State, it only reduces damage.

Resolving Other rolls: Your d20 roll+Related Situation Attribute+Related Situation Skill. So let's say you're negotiating to lower the price of a Rifle. You roll a 11. So, you add your Charisma Attribute (For this example, is 2.), and your Negotiation Skill( For the example, 3.) So 11+2(Charisma)+3(Negotiation)= 16. I will list the situation roll in parentheses at the bottom of each post.