So why couldn't a guy with a bow shoot a badguy who came through the door and sorta moved in his direction?
Because the limitation on the Reaction is that it is reactionary. It is not proactive. Any proactive actions, a character has to do on his action or use the Ready or Delay actions.
Ready and Delay are not replaced by the Reaction. Reaction only takes over some of the duties of the Ready Action.
What about a spellcaster - could he cast a Shocking Grasp spell if someone started coming towards him? What about a Fireball? Confusion?
That's a good question. I would say that no distance attacks could be used, like the bow. But, as long as the casting time of the spell was a Standard Action or shorter, I don't see a reason why a spellcaster couldn't use Shocking Grasp on (I don't know it's casting time--I don't use those spells in my game) on a foe that approaches him. It's a touch spell, yes?
This concept works for me. I imagine Reaction to be a player saying, "Ok, I've moved on my turn, and as my Ready Action, I'm going to be paying attention to anything coming at me so I can do something about it."
Exactly.
"That monster is attacking my Ally over there. Doesn't affect me, so doesn't apply."
Yep.
"That Bandit just jumped out from behind that tree over there. He's looking at me and shouting, but otherwise not approaching. I can't shoot him with my bow in my hand."
Yep.
~Limits of 'Reaction'. Am I getting this right?
Sounds to me like you've got it exactly.
Between a ready and a reaction, I think PCs can do anything. Essentially they can delay their standard action an arbitrary amount of time after they take their move. At least, I can't see any type of (non-restricted) standard action a PC can't take.
With the Ready action, the PC has to name, specifically, what he will do and how his action is triggered.
With the Reaction, the PC does not have to name his action, but his action must be reactionary--in reaction to a threat--and the trigger is the threat on the PC.
See RUMBLETiGER's examples above. Those things are not reactionary to a personal threat. Someone charging you or engaging you in melee are reactionary.
Game-mechanically I'd be worried about this slowing down the game.
Fair comment. But, I don't think so. Here's why.
1 - Since there is no declaration with the Reaction, there's no slowing down the game there because the player isn't thinking about it.
2 - Since the Reaction is reactionary, you never worry about it unless a character who only performed a Move earlier in the round is attacked. If he's not attacked, the Reaction is triggered.
I envision a combat round to play out like this:
Fred has nish. He moves ahead 20 feet, scouting for the party. He's alert, looking, smelling, listening for trouble.
A goblin breaks from the bush, screaming and mashing his teeth, charging Fred.
Fred slams the end of his spear down to the ground as goblin runs towards him. He locks his foot over it, then braces the spear, shoving it in front of him just as the goblin gets to him.
In game terms: Fred made a Move action of 20'.
Then it was the goblin's turn, who saw Fred and charged him.
Since this is a threat to Fred, he can use a Reaction by setting his spear for the charge.
As the goblin approches, Fred attacks first. By the rules, he gets automatic double damage if he hits (setting a spear for a charge). If he misses, well, he didn't react quick enough in time. Now, the goblin proceeds with his charge attack.
One thought: We could limit the Reaction further to only melee attacks if a weapon is at the ready (not in a sheath).
So, the Reaction could be a melee attack or the setting of a weapon for a charge, but nothing else.
Thoughts on that?
I think it would make it harder to close into melee because reactions make eliminate the risk of a readied action to attack an opponent when they close with you goes away.
In RL, it is generally harder to attack than to defend.
instead you pick a reaction. If someone closes to melee with you, you react by attacking them. If something better comes up to react to, you react to that. I've read that concerns over slowing down combat too much is one of the reasons why the designers make you provoke an AoO when you move away from an enemy instead of when you approach them.
What Fred did above can be done by the RAW. He would simply move 20' feet then Ready an action to attack any foe that attacks him in melee. He wouldn't get the double damage (unless he Readied to defend against a charge)...
....but it seems to me that, if you're readied for a charge, you're not that far away from attacking someone who is not charging you but engaging you in regular melee.
Here's another thought: What if you threw away the Reaction action alltogether, but, instead, made a special type of Ready action that allowed you to either attack someone who approached you or set your weapon for a charge.
This way, the rules really aren't changed--you've just broadened a Ready Action. You can attack someone who approaches for melee or you can set for a charge--your choice (because you should have a choice since you have nish).
More generally, I've found it more helpful to think of combat as cyclical, not simultaneous. I think it's a more gamist than a simultaneous-action interpretation, but I think it really fits the rules better as they're written. With the cyclical interpretation there's no concern that the game doesn't model the simultaneity well, because there's no simultaneity to model. I'm not saying your view is wrong or bad, it's just that I don't see the same problem you do.
Well said. And, to be clear, I'm not saying that I see a problem. I'm just investigating something my player said when I was teaching him the Ready Action.
In that discussion, I was the one taking the gamist approach, saying, "Your turn is over!" And, he was saying, "So...what did my character do...just move out into the field and stand there as he saw someone charging him?"
And, he continued, "I have nish. I should have the advantage. So, I should be able to react to a charge. I can see the guy coming at me--but by using this turn method, I don't know as a player what my character would know after one second of looking at the battlefield."
My player has a point. I'm investigating if there is a good solution, or if I should stick with the RAW.
EDIT: I'm 95% sure I'll stick with the RAW. But, I also may revisit this idea later, once I feel I have a better comand over the 3.5 rules.