PRPG->Combat-> Unchained Action Economy

http://www.d20pfsrd.com/gamemastering/other-rules/unchained-action-economy

Summary

Every character gets "3" actions a round and one "Reaction".  These "Actions" can then be spent on different actions that cost different amount of actions to activate (ie Simple[1], Complex[2-3], and Move[1]).  Reactions are used to make AoO's or use immediate effects (yes this means casting feather fall now eats up your AoO. Also means if you take a Reaction to make an AoO you can't also do an immediate action now).  Quick translation from old to new rules.

• Standard Action - Costs 2 acts.
• Swift Action - Costs 1 act. You can do more than one per round.
• Immediate Action - Costs your 1 Reaction per round.
• Full Round Action - Costs 3 acts.
   

This system really seems to add more mobility to characters and more fun options especially martial with a slight debuff to casters as spells take more actions to use.  My take right now is a little more power at low level and less power at higher level. Plus easier for new players because the number of attacks does not change from level 1 to level 20.  You can under this system do some of the following for characters.

• Load a Heavy Crossbow (2 Actions) and shoot (1 action) all in 1 round.
• Move 30ft (1 action) to a creature and get two attacks (1 action per attack) at level 1 at +0/-5!
• Not move at all and get 3 attacks (1 action per attack) at level 1 at +0/-5/-10!
• 5ft step twice (1 action per step) and get a single attack (1 action)
• If you have two weapon fighting you can move 30ft (1 action) and you attack with both weapons (1 action) and then can make a single second attack (1 action) at -5.  Hence why our normal house rule of lowering TWF penalties is not in effect this game.
• Cast a 1 round action spell using 3 actions so that it goes off on the same round you started casting. Also why our houserule of making 1 round spells into full-round actions are not in effect for this game.
• Standard Action spells cost 2 actions and swift action spells cost 1 action.
• A paladin could lay on hands himself 3 times (1 action per LOH) in the same round.  Or LOH x2 (1 action per LOH) and activate smite (1 action).
• Another example using a level 6 paladin normally could activate smite, 5ft step and then get two attacks you can't in the new system. This would cost 1 action to activate smite, 1 action to 5ft step, and 1 action to attack.
• A Warpriest can use fervor 2 times (1 action each to a max of 2 spells a round) in the same round to get two spell buffs up and still attack or move (1 action).  Or activate both his Sacred Weapon & Sacred Armor (1 action each) ability & get an attack off still (1 action).
• Special Note: For spellcasters a unique ability in this new system allows them to cast 3 spells every 2 rounds.  This is accomplished because spellcasting is a Complex action that allows spells to be started on 1 round and finished on the next.  Meaning at end of first round you cast one spell (2 acts) and use your 3rd act to start casting a new spell.  Next round you use 1 act to finish the spell and can still use your 2 acts to cast another spell.
  

Shadow d20 Rules

The following covers a few odd cases in the rules and how UAE interacts with them.

• Rapid Shot works the exact same way as Two-Weapon Fighting/Flurry of Blows.
• Vital Strike can only be used on the first attack action each round.
• Manyshot is only used on the first attack action each round.
• Channel Energy (1 Act): But you only use this ability once per round. Unless you take the feat Quick Channel which allows you to use Channel Energy twice per round.
  
• Warlock Eldritch Blast (Variable): Standard Eldritch Blast is 1 act but by adding any Hex that alters the Eldritch Blast the action type is changed to complex action and costs 2 acts.
• Total Defense (2 Acts): You concentrate on defense rather than attacking. Until the start of your next turn, you can't take actions with the attack subtype, and you gain a +4 dodge bonus to AC.  If you have at least 3 ranks in Acrobatics the bonus increases to +6. Total defense can not be activated after you have taken an attack action but other actions (ie move) are allowed.
• Ready a Simple Action or an Advanced Action (0 Acts): You ready a single simple or advanced action that you can take before the start of your next turn as a extra reaction (this does not use up your normal reaction) . You must designate a definite trigger for that reaction (such as "if a foe attacks me," "if a foe casts a spell," or "if a foe moves adjacent to me"), and you must have enough acts left to complete the action you ready. Once you ready an action, your turn ends. If you don't take the action you readied as an extra reaction by the start of your next turn, you lose that extra reaction. If this extra reaction is a type of attack it is at the normal penalty for the round.  In example if you make two attacks and ready a third attack as a your Ready Action it will go off at a -10 penalty.
  
• Pounce (3 Acts): A creature with this special attack can move up to double its base movement speed by taking a -2 AC penalty and at the end of its movement it can make all its natural attacks vs a single target.
• Cantrips [0 Level Spells] ( 1 Act): Cantrips for all classes will be a single action not two like normal spells.  For spells that make "attack" rolls they will be considered simple attack actions meaning they can be combined with Haste.
  
• Natural Attacks
• When a monster has the same natural attack "type" (ie Claws, Bites) they work with the same rules as two-weapon fighting with a maximum of 4 attacks per act. In example a cat has Claw, Claw, Bite.  With 1 act the cat can Claw & Claw.  Then as a 2nd act it can Bite.
• If you use a manufactured weapon and a natural attack (ie skeleton with scimitar and claw) this also acts like TWF and allows for the skeleton to claw attack and scimitar attack with one act.  This would be the same for a barbarian with the Bite Rage power.

Conditions

• Staggered: A staggered creature may take only a single action each round. A creature with nonlethal damage exactly equal to its current hit points gains the staggered condition.

• Nauseated: Creatures with the nauseated condition experience stomach distress. Nauseated creatures are unable to attack, cast spells, concentrate on spells, or do anything else requiring attention. When nauseated you have a single action per round which can only used for simply actions without the "attack" subtype.  In addition you can not cast or begin to cast any spells.

• Disabled: A character with 0 hit points, or one who has negative hit points but has become stable and conscious, is disabled. A disabled character may take a single action each round and moves at half speed. Taking subtype actions of "move" doesn't risk further injury, but performing any other subtype of action (or any other action the GM deems strenuous, including some swift actions such as casting a Quicken Spell spell) deals 1 point of damage after the completion of the act. Unless the action increased the disabled character's hit points, he is now in negative hit points and dying.
• A disabled character with negative hit points recovers hit points naturally if he is being helped. Otherwise, each day he can attempt a DC 10 Constitution check after resting for 8 hours, to begin recovering hit points naturally. The character takes a penalty on this roll equal to his negative hit point total. Failing this check causes the character to lose 1 hit point, but this does not cause the character to become unconscious. Once a character makes this check, he continues to heal naturally and is no longer in danger of losing hit points naturally.