[Action 2:Exploits] BAD and ACT?

[Ultraviolet]

I'm trying to wrap my head completely around this system, and it seems simple and fast-paced.

But I have a question about ACT: It is a bonus the PCs can accumilate to counteract the BAD. But the description is somewhat vague on GURPS Action 2: Exploits p17, referring only to the Big Picture, the Plan and Permission to ACT.
Shouldn't the prep-work reduce the BAD during execution of the plan?

Also, there are many fine hints as how to run fact-finding and social engineering etc, for the prep-work. But how much ACT is gained by each scene playes? Any rules, or just GM fiat? I see that failure means an excuse for a fight, chase, or otherwise a tip-off of the bad guys that the heroes are coming. But for a succes? It it simply a drive towards the next plot development?

[Kromm]

Here's how it works:

1. Fact-Finding. ACT stands for "Accumulated Complementary Total" because it's the sum of all complementary skill roll modifiers (+2 for critical success, +1 for success, -1 for failure, -2 for critical failure) generated by rolls to gather information about the next act in the story. Any roll that leads to a clue about that act (true or false!) contributes. Research, hacking, interrogation, wiretaps, you name it . . . the only restriction is that success with the skill involved could plausibly yield a fact.

2. Analysis. Clues must be analyzed by making the roll under The Big Picture. That roll is at a bonus equal to ACT and a penalty equal to not BAD per se but some multiple of BAD set by the GM: BAD, 1.5×BAD, 2×BAD, or whatever. Critical success reveals what's going on and allows planning at +2; success allows planning at no bonus; failure allows no planning and means the group must gain at least another +1 to ACT to try analysis again; and critical failure works like failure, plus the group is sidelined into kicking down the wrong door, fighting the wrong people, etc.

(2a. Permission. In some campaigns, there's an AR here that has the same modifiers as the analysis roll. Success means the group is cleared to go on to the next step. Failure means they aren't. Where this AR replaces the analysis roll, assume the patron organization does the analysis once it gets enough clues from the PCs.)

3. Planning. Successful analysis allows the planning roll under The Mission Plan. This is also at a bonus equal to ACT and a penalty equal to a multiple of BAD set by the GM, but now there's a possible +2 for critical success at analysis and potential bonuses for complementary skill rolls against planning skills. Succeed or fail, this roll allows the group to tackle the next act . . .

4. Execution. All rolls made in the field are subject to BAD for this act, but the planning roll acts as a complementary skill roll to all of these rolls, effectively adjusting BAD.

In other words, ACT never directly cancels BAD in the field. ACT cancels BAD-related penalties to rolls for analysis, permission, and planning. Success pays forward to the next step as a complementary bonus: good fact-finding makes analysis easier, good analysis makes planning easier, and good planning makes field tasks easier. Thus, the maximum offset to BAD for field tasks is +2, when the planning roll critically succeeds. ACT is not a general way to make field tasks easier.

I think what's confusing is that BAD is used in two different ways: as the basis for penalties to analysis and planning, and as a direct penalty to field tasks. ACT is only directly relevant to the first of these.

[Ultraviolet]

A big thanks to Dr. Kromm for a speedy and comprehensive answer.

I do have a follow up question: What about the phase of Preparing?

For when the action heroes get hold of the tools, vehicles, guns, wierd equipment, hacker assistance for records to back up fake IDs they need to pull off the plan?

Strictly put this shold come in between the Plan and Execution. But the scenario I'm planning may have some of these Preparation scenes happen while they're gathering intel to begin with, fot thinghs they know they need (recruiting the help af a hacker).
Timing may not be the greatest issue regarding the Action: Exploits system.

However the mechanics?
Something along the lines of: If the Plan requires certain equipment Executing is is modified by BAD but Complementary Skills can offset this penalty by actually getting these things?
Say the infiltration plans for two guys to dress up as electricians and act as they are there to fix a problem, and in the proces plant a bug or sabotage the alarm or whatever.
So they need a van from the electric company, tolls and uniforms, fake work orders. Getting these things sound like Preparing to me, or is it covered somehwere else I just haven't seen?

[Kromm]

Preparing is covered by planning. That's why The Mission Plan opens with this:

Action-movie planning ranges from "Synchronize watches!" to an entire montage of equipping, mapping, rehearsing, etc.

Simply put, you can't blow away high BAD with prep. That isn't how it works. High BAD calls for high skill, though planning can help a little (up to +2), and a lot of gear gives specific additional bonuses (e.g., +1 or +2 for good- or fine-quality gear, +1 to science skills for a field lab, etc.). As the rules for BAD say:

The only other modifiers that apply are those that the PCs bring into the picture: bonuses for equipment, penalties for disadvantages, etc.

If BAD is too steep for the heroes to handle, they need to work more slowly (bonuses for extra time), bring better gear (bonuses for equipment), and make more complementary skill rolls (bonuses for assistants). These are the things that BAD abstracts for the other side, remember:

As with all BAD things, this is abstract. Actual skill, equipment quality, extra time, and anything else that might matter is all rolled into one handy number.

This stuff isn't left abstract for the heroes, though! Still, the GM should remember what it says under From BAD to Worse:

However, BAD doesn't always get worse. If the crew scores a coup – e.g., steals files containing the names of the corrupt cops and the technical specs for the station's security system – then the next part of the adventure might be easier.