1.0 Rules

Rolls
Whenever you try to do something that takes effort and that isn’t walking, you’ll probably have to make an ability check to pull it off. When you make an ability check, the DM sets the so-called DC (difficulty class) of the action you’re attempting. You then roll d20 and add the appropriate ability score. If the result equals or exceeds the DC, the action succeeds. Attacks resemble ability checks, and are discussed under the Combat header.

Opposed checks: An opposed check means that two creatures make a check and then compare results to see who won. If they both roll the same value, roll again until a winner emerges.

Advantage and disadvantage
When making an attack or check under hindering circumstances, you have so-called disadvantage, meaning you roll two d20s instead of one and must use the lower roll. If the circumstances work in your favour, you have advantage, meaning you roll two d20s and use the higher roll. If both advantage and disadvantage apply, they cancel each other out and you roll normally. If more than one case of the same applies, it stacks, causing you to roll three or more dice and take the highest/lowest one. This is called double/triple (dis)advantage.

Common things that provide advantage: Common things that provide disadvantage:
 * Attacking a prone target
 * Attacking a target that’s unaware of you
 * Attacking when downed
 * Attacking a target with cover or concealment
 * Attacking with an improvised weapon

Turns
Every battle starts by rolling initiative. That means every creature makes an intelligence check (d20 + int), the outcomes of which determine the turn order, with the highest roll getting their turn first.

Each round in combat represents about 6 seconds. Every round, each participant gets two actions.

Actions
An action can be spent to either move up to your speed or to make an attack. They don’t have to be self-isolated: you can, for example, move half your speed, attack, then move the other half. To spend both your actions attacking is called a full attack. There are many other actions you could take. Anything one could do in real life, and then some, is possible in-game, at the DM’s discretion. Some actions are full-round actions, which means they take up both of your actions for the round.

Free actions
Free actions can be used indefinitely, up to a reasonable extent. Most simple action, such as picking up an item or handing an item to someone are free actions, at the DM's discretion. As a general rule, you can do one such action for free every turn. You can draw one two-handed or two one-handed weapons (including shields) as a free action, but sheathing one weapon and drawing another in one turn requires a standard action. Very easy actions, such as talking or drawing an arrow from your quiver, can be done nigh-indefinitely.

Sneaky steps
If you spend your turn only making non-movement actions, such as a full attack, you may move one square for free at any point during your turn. This is called a sneaky step.

Attacking
Whenever you make an attack against an enemy, you roll d20 and add the relevant stat, and possibly other modifiers. If the result equals or exceeds the target’s defence, you score a hit and deal damage according to your weapon type and strength score. Most attack rolls look like this:
 * Melee attack: d20 + strength (or d20 + dexterity when using a finesse weapon)
 * Ranged attack: d20 + dexterity – range penalty

Range penalties
Ranged attacks have a range increment, the distance they can cover before taking penalties on the attack roll. An attack with a range increment of X takes a -1 penalty for every X squares between attacker and target. Usually, projectile weapons have a range increment of 8 squares and thrown weapons 4 squares. Projectile weapons have a maximum range of 10 increments, thrown weapons 5 increments.

You also disadvantage on ranged attacks if any enemy is adjacent to you, whether they're the target of the attack or not.

Crits and crit fails
When making an attack roll, if the die lands on a 1, the attack is an automatic miss. This is called a crit fail. If the die lands on a 20, it’s an automatic hit, and you deal double damage. This is called a crit. At the DM’s discretion, a crit or crit fail may cause additional effects.

Combat maneuvers
There are many other things you can do in combat beside standard attacking. You can push your opponents around, trip em, disarm em, etc. I’m sure there’s many more tricks you guys can think of that I wouldn’t have, and that’s the beauty of it. Combat maneuvers, as they’re called, are usually resolved as opposed ability checks. Whenever a rule (e.g. the opportunity attacks rule below) says you can make an attack, you may usually substitute a combat maneuver, at the DM’s discretion.

Readying actions
During your turn, you can choose to ready an action. In this case, you specify a condition and an action. If, between the end of your current turn and the start of your next, the condition is fulfilled, you execute the action. Example: “If an enemy approaches me, I make a melee attack against them.” This allows you to act outside of your turn, but you have to give up an action in your current turn to do it. If the condition doesn’t occur, the action is wasted.

Elements
There are five elements: physical, fire, frost, lightning and poison. Any attack without a stated element is physical. Certain creatures are vulnerable, resistant or immune to certain elements. Attacking with an element that the target is vulnerable to deals 1.5x the damage. If the target is resistant, it deals only half damage. If immune, it deals no damage at all.

Action surges
Every player character has a single action surge per day (or rather per rest, see below). An action surge is meant to be used in combat, to turn the tide of battle when it's most needed. By using your action surge, you can either gain one extra action on your turn, or one action outside your turn, interrupting the current creature's turn as if you'd readied the action beforehand. If the out-of-turn action is a non-move action, you may take a sneaky step as part of your action surge, without expending your sneaky step for that round.

Injury and recovery
If your HP reaches 0, you’re knocked unconscious and are near death. After three rounds of unconsciousness, you bleed out and die. This can be prevented if one of your allies spends a full-round action to stabilize you. When stabilized, you remain at 0 HP, but are safe from bleeding out. You will regain consciousness when your HP is healed back to 1 or higher. A near-death character, stabilized or not, can be finished off by a single successful attack.

You can regain HP by resting. To take a rest, you must spend eight hours in a safe location while undertaking no strenuous activity. Getting a night’s sleep, basically. After a rest, you regain your action surge, any "per rest" abilities, and 20% of your max HP.

Rounding
Whenever a formula results in a fraction, you always round down.

Effect durations
Effects with a set duration always end at the start of the turn of the creature who caused the effect. Effects with a duration of one round end at the start of the caster’s next turn, those with a duration of two end at the start of the turn after that, etc.