In a typical pen and paper RPG system, characters usually go in turns. After rolling a die to see who goes in what order, a character will usually do all of his actions and then it will be the next person's turn. Some systems try to add tactics to this by having an "attack of opportunity" system that allows players to make limited attacks out-of-turn. However, these systems are almost always very difficult to remember except for the most experienced of players!
In an attempt to both allow characters more realistic reactions to what's going on around them in combat, and also add a bit of a tactical flare, I decided to implement the action point system I briefly went over in the previous post. You can blame me being on a mechanics bent this last week on action points, coming up with them really excited me!
Basically, dice will still be rolled to determine what order the characters' and players' turns will be. However...
When it's a player's turn, he'll be able to do actions, spending action points for every action he does. Certain actions take more action points, certain actions take less - and this is usually dependent on how long those actions take to preform.
Most actions will cost either 1 action point, 2 action points, or 3 action points. A short jab that does very little damage will cost 1 action point, as will drawing or sheathing a weapon, or firing a pre-prepared projectile weapon. A standard attack that has a chance of dealing critical damage will cost 2 action points, as well taking a five-foot step or drawing a bow. A three action point activity would be quafing a potion, making a deathblow attack (that is guranteed to do significant critical damage), casting a spell, reloading a crossbow or reading from a scroll.
The key to this system is that characters can act out of turn in a very simple way, that's easy to remember. During another character's turn, you can interrupt their turn when they spend 2 or more action points at once. This is called a "Sequence interrupt" and during this interrupt you can spend action points to do actions of your own. The catch is, the actions your character does must cost one less action point than the current action being performed by the character whose turn it is. Conceptually, you're doing your action while they're busy with their action, which takes longer to perform.
For instance, if another character is attacking your character with a 3 point deathblow, your character can attack them preemptively using two jabs, or a single standard attack. Your character could also even simply take a 5 foot step away, and cause the deathblow attack to miss completely!
Other examples: If another character that you're flanking decides to take a 5 foot step away, you can attack them with a quick jab. If another character is trying to cast a spell, you can attack them to try to disrupt the spell.
There are limits to when sequence interrupts can be done however. Characters with ranged weapons can sequence interrupt just about anyone, but only if they're firing their weapon at the character whose turn it is. Characters with melee weapons can only sequence interrupt when they are being attacked directly, or when they are flanking the character whose turn it is. If a melee character is being flanked, he cannot sequence interrupt, and he can barely defend himself.
Of course, sequence interrupts are optional. You don't have to take advantage of them if you don't want to spend your action points - however, attacks done during a sequence interrupt have far less options for defense than normal, and usually, if the person whose turn it is decides to defend themselves from your sequence interrupt attack, their action may literally be interrupted and not get followed through.
Speaking of defense, defensive actions also cost action points, and doing them doesn't count as a sequence interrupt. The core defensive actions (dodging, parrying/riposting, and blocking) all cost a single action point, so it's important to end your turn with an action point or two left over, so you can defend yourself from attacks.
Finally, move actions are a little different. Whenever moving across the battlefield, the first 5 foot step costs 2 action points. After that, every single action point you spend will allow you to move an additional number of 5 foot squares equal to your agility score. The entire move action thus will count as 2 action points for anyone you are disengaging from, but 3 action points (at least) for anyone who sees you coming, who might be able to take a swipe at you as you pass them or before you engage them. You can also sprint - and move twice your agility for every aditional action point spent, but this causes you to lose endurance points.
I hope this has all made sense! The ideas are all still fairly new, so I haven't yet figured out the best way to present them, but I'm glad to have gotten them down into the blog.