The difference between reactive and proactive can be really blurred here. Aren't you reacting to the swinging platform coming near to you?
I think that depends. Are you expecting the platform to perform a repetitive action? Or is the platform movement unpredictable? If we're talking Mario here and the platforms are simply moving nearer and further in a consistent pattern, I don't consider this to be a reaction. You are doing the math in your head while your wait, and then jumping. If we're talking about the lands of chaos where there is no ryhme or reason to the movement, that is definitely reactionary.
If you know that the floor is about to drop away beneath you because you've triggered a trap, aren't you proactively jumping away from it in the sense that you anticipate a problem and actively jumping away and reacting to stimulus all at the same time? Proactive activity is generally defined by its preparation and taking control of the situation. So, tying a rope around your waist and securing it to some belay before you jump is clearly proactive. Digging a foxhole when you aren't yet in contact with the enemy is clearly proactive. Timing a jump to a narrow window is well a very blurry case, but in general I wouldn't define it as being in control of the situation or acting in a preparatory way. A more proactive move might be using a grappling hook to try to alter the motion of the platforms.
Sure, and as I mention later, for several of those situations, your life in not in danger while you are attempting to make the action. And that's the deliniation I attempted to make. If there is a clear and present danger, then your hand is forced and you are
reacting. If the danger is vague or distant, then you are
proacting.
Checks are more often than not active rather than proactive, and in general the cases here are so blurry that I don't find your distinctions particularly useful.
They don't really have to be I suppose. They make sense in my head and I'm the one using them. As a player at your table, I think there's a potential for me to make an argument based on my current situation as to if I am
reacting to
proacting.
So suppose that when each platform reached its closest point to the next, it dropped off, which would be defined as something bad happening to you, is it now a reflex save? Suppose you only thought that the platform was about to collapse, what is it?
That depends on when you make your jump. If you are planning your jump to take place at the last minute, it is proactive. If you are making your jump because you didn't realize the platform was dropping off, that is reacting. Again, it's a matter of preparation. When your hand is forced and you cannot take the time to prepare, you are reacting.
Suppose we slightly alter the scenario. You are now running down a collapsing bridge or causeway, leaping from stone pillar to stone pillar, just before the one behind you collapses. Is this now reactive or is it still proactive? It's the exact same ability being used whether or not the pillar you are currently on is going to fall 1 round from now or two or ten.
No, I think that the time you have before collapse certainly makes a difference, as if you have several rounds to make your jump, you have time to prepare, even if the time is limited. If we were to say that the pillar began to collapse the moment you landed on it, and would fall away the next round, that is a reaction. If the pillar began to collapse the moment you landed on it, but it took 5 rounds, that can be pro-acted to.
I find that to be a particularly tedious and situational way to look at things.
I quite like viewing things as situational. It can keep the same concept fresh by having each instance of it treated differently. As with the pillar example above. You can be exploring two different segments of a dungeon, each with collapsing halls and pillars, but because their rate of collapse is different, it makes your treatment of the situation different. Perhaps because the pillars in Room 2 are sturdier and thus take 5 rounds to collapse, you tie a rope around Bob the Ninja, who jumps quickly across and secures the line so that Joe, Jenny and Jimmy can have something to hang on to, even while they jump from pillar to pillar, reducing the DC of their jump check, and providing security in case one of them falls.
The same situation of collapsing halls was now made more pro-active and was resolved completely differently simply because the party had more time to prepare.
I quite like granularity and situationalism. Otherwise the game becomes repetitious or puts an unrealistic demand on the DM to create wholly unique situations when really, a collapsing tunnel would be pretty common in an old dungeon, cavern, mine, tomb or any other unstable structure.