Thursday, October 30, 2014

Unified Stealth/Surprise Table


Sneaking is a good Halloween subject, as it is the season to do so, in good fun.


There was a pile of discussion earlier on Autarch's boards about thief skills  and the utility thereof. Lots of good ideas in there. One thing that came out of that was the proper methods by which one sneaks - a thief applies Hide in Shadows & Move Silently when applicable, and the targets get Hide Noise and Surprise rolls, when needed.

The process was expounded upon, resulting in a few 'choice trees' - CharlesDM of the excellent By This Axe I rule blog has one here, in fact.

Since we're dealing with dice, we're dealing with percentages which means we can simplify this down to scorched earth.

And I do so, on the table below. Note I've added another choice to the tree - the choice to Move Silently towards an inattentive target, so as to deny them a Hear Noise roll.

We'll proceed assuming my second time through Statistics stuck. ;)


Attentive Target
Inattentive Target
Concealment
No Concealment
Hide Successful
Hide Failure
Move Silently Successful
Move Silently Failure
Move Silently Successful
Move Silently Failure
Hear Noise Failure
Hear Noise Success
Hear Noise Failure
Hear Noise Success
Surprise FailureSurprise FailureSurprise FailureSurprise Failure
Surprise!Surprise!Surprise!Surprise!Surprise!Surprise!Surprise!Surprise!
Anyone---33.33%33.33%-85.00%5.00%
Barbarian---50.00%50.00%-85.00%7.50%
Thief 12.00%6.80%0.40%30.00%33.33%20.00%68.00%4.00%
Thief 23.75%9.56%0.56%28.33%33.33%25.00%63.75%3.75%
Thief 36.00%11.90%0.70%26.66%33.33%30.00%59.50%3.50%
Thief 48.75%13.81%0.81%25.00%33.33%35.00%55.25%3.25%
Thief 512.00%15.30%0.90%23.33%33.33%40.00%51.00%3.00%
Thief 615.75%16.36%0.96%21.66%33.33%45.00%46.75%2.75%
Thief 724.75%17.21%1.01%18.33%33.33%55.00%38.25%2.25%
Thief 835.75%16.36%0.96%15.00%33.33%65.00%29.75%1.75%
Thief 948.75%13.81%0.81%11.67%33.33%75.00%21.25%1.25%
Thief 1063.75%9.56%0.56%8.33%33.33%85.00%12.75%0.75%
Thief 1180.75%3.61%0.21%5.00%33.33%95.00%4.25%0.25%
Thief 1285.50%3.83%0.22%3.33%33.33%95.00%4.25%0.25%
Thief 1395.00%0.00%0.00%1.67%33.33%100.00%0.00%0.00%
Thief 14100.00%0.00%0.00%0.00%33.33%100.00%0.00%0.00%


This is a Plinko game of possible ways to get surprise on someone. Drop from Attentive Target to a Hide Success to a Move Silent Failure to a Hear Noise Failure, and you know your 5th level Thief has a 15.3% chance to get surprise in that particular situation.

Check out Thief 14. Note how there's a bunch of 0% chances in there - that's the chance to get into that particular situation - we never do, because the Thief does not fail her checks at that level. That leads us to our next table.

The thing about percentages is that different choices at different rates of success to get to the same result are additive - so we can simplify this further, if we don't care how the result was had:

Target Without AlertnessTarget Has Alertness
Attentive TargetInattentive TargetAttentive TargetInattentive Target
ConcealmentNo ConcealmentConcealmentNo Concealment
Anyone33.33%33.33%90.00%16.67%16.67%70.83%
Barbarian50.00%50.00%92.50%33.33%33.33%76.67%
Thief 139.20%33.33%92.00%22.67%16.67%76.67%
Thief 242.21%33.33%92.50%25.89%16.67%78.13%
Thief 345.26%33.33%93.00%29.25%16.67%79.58%
Thief 448.37%33.33%93.50%32.76%16.67%81.04%
Thief 551.53%33.33%94.00%36.42%16.67%82.50%
Thief 654.74%33.33%94.50%40.22%16.67%83.96%
Thief 761.31%33.33%95.50%48.26%16.67%86.88%
Thief 868.07%33.33%96.50%56.89%16.67%89.79%
Thief 975.04%33.33%97.50%66.09%16.67%92.71%
Thief 1082.21%33.33%98.50%75.89%16.67%95.63%
Thief 1189.57%33.33%99.50%86.26%16.67%98.54%
Thief 1292.88%33.33%99.50%90.35%16.67%98.54%
Thief 1396.67%33.33%100.00%95.83%16.67%100.00%
Thief 14100.00%33.33%100.00%100.00%16.67%100.00%

As Judge, I have exactly three decisions - does the target have Alertness, is the target Attentive, is Concealment available - then I roll my percentile single surprise roll for that particular situation or round of movement.

This brings out some interesting things. Barbarian's Naturally Stealthy is a heck of a bonus - pushing the Barbarian's chance to surprise a foe up to the same level as a 5th level Thief sneaking her heart out. (we can safely assume the Barbarian always fails his Hide In Shadows check, hence he has his normal chance to surprise the opponent).

If I really wanted to know how the thief managed to surprise her target, I could set up a table assigning ranges to different percent spreads, drawing from the first table. If I was willing to give up some resolution on the results, I could drag this back down into a d20 table (which I'll probably do before I actually use this).

Since I have the spreadsheets up, I can take a moment to look at a few different possiblities. In the thread on Autarch's board that spawned all this, Alex posted a set of house rules to improve the thief's chances via equipment bonuses and encumberance advantages.

All in all, the maximal bonus a thief can get to Hide in Shadows and Move Silently is +6 each. What's that look like?

Target Without AlertnessTarget Has Alertness
Attentive TargetInattentive TargetAttentive TargetInattentive Target
ConcealmentNo ConcealmentConcealmentNo Concealment
Anyone33.33%33.33%76.67%16.67%16.67%70.83%
Barbarian50.00%50.00%82.50%33.33%33.33%76.67%
Thief 155.33%33.33%88.33%44.17%16.67%85.42%
Thief 258.61%33.33%89.50%48.26%16.67%86.88%
Thief 362.00%33.33%90.67%52.50%16.67%88.33%
Thief 465.51%33.33%91.83%56.89%16.67%89.79%
Thief 569.13%33.33%93.00%61.42%16.67%91.25%
Thief 672.87%33.33%94.17%66.09%16.67%92.71%
Thief 780.71%33.33%96.50%75.89%16.67%95.63%
Thief 889.01%33.33%98.83%86.26%16.67%98.54%
Thief 996.67%33.33%100.00%95.83%16.67%100.00%
Thief 10100.00%33.33%100.00%100.00%16.67%100.00%
Thief 11100.00%33.33%100.00%100.00%16.67%100.00%
Thief 12100.00%33.33%100.00%100.00%16.67%100.00%
Thief 13100.00%33.33%100.00%100.00%16.67%100.00%
Thief 14100.00%33.33%100.00%100.00%16.67%100.00%

Quite a bit better. A city thief who's not running out of armor oil in the middle of a dungeon can make a pretty good go of things right off, beating the Barbarian immediately. That table also models somewhat what would happen if a DEX 18 Thief was allowed to add her bonus to the rolls, and had taken the two proficiencies improving the skills, for a +5 total to each.

Moving on, what happens if we let Naturally Stealthy be a general proficiency, so anyone can take it, including thieves and other folks with stealth skills?

Target Without AlertnessTarget Has Alertness
Attentive TargetInattentive TargetAttentive TargetInattentive Target
ConcealmentNo ConcealmentConcealmentNo Concealment
Anyone50.00%50.00%92.50%33.33%33.33%76.67%
Barbarian50.00%50.00%92.50%33.33%33.33%76.67%
Thief 154.40%50.00%94.00%38.13%33.33%81.33%
Thief 256.66%50.00%94.38%40.71%33.33%82.50%
Thief 358.95%50.00%94.75%43.40%33.33%83.67%
Thief 461.28%50.00%95.13%46.21%33.33%84.83%
Thief 563.65%50.00%95.50%49.13%33.33%86.00%
Thief 666.06%50.00%95.88%52.17%33.33%87.17%
Thief 770.98%50.00%96.63%58.61%33.33%89.50%
Thief 876.06%50.00%97.38%65.51%33.33%91.83%
Thief 981.28%50.00%98.13%72.87%33.33%94.17%
Thief 1086.66%50.00%98.88%80.71%33.33%96.50%
Thief 1192.18%50.00%99.63%89.01%33.33%98.83%
Thief 1294.66%50.00%99.63%92.28%33.33%98.83%
Thief 1397.50%50.00%100.00%96.67%33.33%100.00%
Thief 14100.00%50.00%100.00%100.00%33.33%100.00%

Gives a good improvement, but doesn't have that sudden jump at the end that happens with the equipment/encumberance rules.  It'd be a heck of a lot better than the proficiencies that give +2 to the skills.

Let's do a couple more question-answerings. What happens if we let anyone try to Hide in Shadows or Move Silently, at one less point on the die than a level 1 Thief?

Target Without AlertnessTarget Has Alertness
Attentive TargetInattentive TargetAttentive TargetInattentive Target
ConcealmentNo ConcealmentConcealmentNo Concealment
Anyone36.24%33.33%91.50%19.59%16.67%75.21%
Barbarian52.18%50.00%93.63%35.67%33.33%80.17%
Thief 139.20%33.33%92.00%22.67%16.67%76.67%
Thief 242.21%33.33%92.50%25.89%16.67%78.13%
Thief 345.26%33.33%93.00%29.25%16.67%79.58%
Thief 448.37%33.33%93.50%32.76%16.67%81.04%
Thief 551.53%33.33%94.00%36.42%16.67%82.50%
Thief 654.74%33.33%94.50%40.22%16.67%83.96%
Thief 761.31%33.33%95.50%48.26%16.67%86.88%
Thief 868.07%33.33%96.50%56.89%16.67%89.79%
Thief 975.04%33.33%97.50%66.09%16.67%92.71%
Thief 1082.21%33.33%98.50%75.89%16.67%95.63%
Thief 1189.57%33.33%99.50%86.26%16.67%98.54%
Thief 1292.88%33.33%99.50%90.35%16.67%98.54%
Thief 1396.67%33.33%100.00%95.83%16.67%100.00%
Thief 14100.00%33.33%100.00%100.00%16.67%100.00%

A couple percent point improvement for the non-thief classes; theoretically cheap to implement if you're OK with using this table.

One more - there's a few thoughts floating around about combining Move Silently and Hide In Shadows into one single 'Stealth' or 'Skulking' skill roll. What happens if we remove the barrier to success that is requiring two successful rolls?

Attentive Target
Inattentive Target
Concealment
No Concealment
Stealth Failure (Same as No Concealment)
Stealth Successful
Stealth Failure
Stealth Successful
Stealth Failure
Hear Noise Failure
Hear Noise Success
Hear Noise Failure
Hear Noise Success
Surprise FailureSurprise FailureSurprise FailureSurprise Failure
Surprise!Surprise!Surprise!Surprise!Surprise!Surprise!Surprise!Surprise!
Anyone15.00%72.25%4.25%33.33%33.33%15.00%72.25%4.25%
Barbarian15.00%72.25%6.38%50.00%50.00%15.00%72.25%6.38%
Thief 120.00%68.00%4.00%33.33%33.33%20.00%68.00%4.00%
Thief 225.00%63.75%3.75%33.33%33.33%25.00%63.75%3.75%
Thief 330.00%59.50%3.50%33.33%33.33%30.00%59.50%3.50%
Thief 435.00%55.25%3.25%33.33%33.33%35.00%55.25%3.25%
Thief 540.00%51.00%3.00%33.33%33.33%40.00%51.00%3.00%
Thief 645.00%46.75%2.75%33.33%33.33%45.00%46.75%2.75%
Thief 755.00%38.25%2.25%33.33%33.33%55.00%38.25%2.25%
Thief 865.00%29.75%1.75%33.33%33.33%65.00%29.75%1.75%
Thief 975.00%21.25%1.25%33.33%33.33%75.00%21.25%1.25%
Thief 1085.00%12.75%0.75%33.33%33.33%85.00%12.75%0.75%
Thief 1195.00%4.25%0.25%33.33%33.33%95.00%4.25%0.25%
Thief 1295.00%4.25%0.25%33.33%33.33%95.00%4.25%0.25%
Thief 13100.00%0.00%0.00%33.33%33.33%100.00%0.00%0.00%
Thief 14100.00%0.00%0.00%33.33%33.33%100.00%0.00%0.00%

That's quite a boost! A failure in Stealth gets boiled down to being the same as having no concealment, and Hear Noise becomes a much less effective gateway. Our combined tables look like so:

Target Without AlertnessTarget Has Alertness
Attentive TargetInattentive TargetAttentive TargetInattentive Target
ConcealmentNo ConcealmentConcealmentNo Concealment
Anyone91.50%33.33%91.50%75.21%16.67%75.21%
Barbarian93.63%50.00%93.63%80.17%33.33%80.17%
Thief 192.00%33.33%92.00%76.67%16.67%76.67%
Thief 292.50%33.33%92.50%78.13%16.67%78.13%
Thief 393.00%33.33%93.00%79.58%16.67%79.58%
Thief 493.50%33.33%93.50%81.04%16.67%81.04%
Thief 594.00%33.33%94.00%82.50%16.67%82.50%
Thief 694.50%33.33%94.50%83.96%16.67%83.96%
Thief 795.50%33.33%95.50%86.88%16.67%86.88%
Thief 896.50%33.33%96.50%89.79%16.67%89.79%
Thief 997.50%33.33%97.50%92.71%16.67%92.71%
Thief 1098.50%33.33%98.50%95.63%16.67%95.63%
Thief 1199.50%33.33%99.50%98.54%16.67%98.54%
Thief 1299.50%33.33%99.50%98.54%16.67%98.54%
Thief 13100.00%33.33%100.00%100.00%16.67%100.00%
Thief 14100.00%33.33%100.00%100.00%16.67%100.00%

That's...excessive. The system sort of falls apart, because Hear Noise's high failure rate is really relying on the combined low percentage chance of both Hide in Shadows and Move Silently needing to be successful - since we don't have a check for "seeing something" other than determining the alertness level of the target. You'd almost have to give being "alert" a throw (like d20 did with Spot) or transmogrify Hear Noise into a general "Notice" throw at a better chance of success.

Even if you reversed Hear Noise so that it succeeded on a throw of 5+, you're still going to have a straight improvement from a base of around 54%, rather than the gradual, curved improvement afforded by requiring two separate rolls.

You may have to then fall back to opposed rolls. Not sure - I'm gonna let that lie outside the scope of this post.



What's the takeaway?

If you look at it as a whole process, it's not as bad as the numbers on the Thief table make it seem. Just being a Thief gets you a better chance to surprise an opponent than a normal person right off. From that view, it's no better or worse than the fighter's Attack Throw at level one - better than a normal man, but not superheroic by any means.

And, for those that want to fiddle, even as much as a +6 bonus doesn't end up being much more than a 20%  improvement level-by-level during the first ~9 levels - and letting anyone attempt to sneak at a tick worse than a level 1 Thief doesn't change things much.

On the other hand, combining Move Silently and Hide in Shadows certainly makes a change for the worse (depending on your view) as it relegates Hear Noise to a much lesser role.


.

4 comments:

  1. I've read the rules over a few times (I've actually been hacking a lot of ACKS into my DCC the last couple years), read the By This Axe post & this post & am *still* not clear on the procedure for determining surprise & how it interacts with MS & HS. I *thought* I understood it, but both of these posts have made it clear that I don't.

    Very frustrating because I hope to start a pure ACKS game soon & need to get this down. I wish there was a video out there of someone stepping though the procedures...

    ReplyDelete
    Replies
    1. Sure. I'm not too hip on video but I could probably whip up a more graphical flowchart sort of thingy - something usable at the table?

      Delete
  2. That would be pretty great. I'm guessing there's something the BTA post is trying to convey that could be improved on with better formatting capabilities.

    I could ask specific questions too, but might have fewer foolish questions with a better head start.

    ReplyDelete
    Replies
    1. :)

      Alright. Lemme put some thought at it; when the next post hits it'll be that.

      Delete