Years ago I put together and ran an adventure using d20 3.0 Modern rules set.  It was okay at the time, but it's too crunchy for my tase now.  I've been repvamping the adventure and rewrote it to take place in the 1980s.  It's about hikers that come across the aftermath of a crime.  The supernatural plays a role too.

I running play tests for part of it with a few groups and then at Total Con in February and at Rising Phoenix's Con in April.  ( I wrote my own rules lightish d20 system.) I'll make the needed adjustments and then release it on DriveThru RPG -  However, I am not ready to release my d20 rules light system yet - so I want to release the adventure on DriveThru with either a modern era system or something that can be run for any era.  I did this with a fantasy adventure, The Murk's Curse, releasing it as compatible with Old School Essentials (I've played lots of B/X D&D, so it was a good fit).  I believe saying it OSE compatible on the cover, but also describing that it works with lots of rules light systems helped me gain some visibility and get some sales.

The Question:  What d20 system modern/generic (rules lightish) would make the most sense to release an adventure like this under?  Why? (Eventually, I'll include it in my system, but that will be a while.)

Thanks.

If you're looking for a lite D20, check out Core Elements Toolbox:

Classic 6 atts
Levels, but no classes
20 skills
No feats
Spells are skill checks

I doubt anyone is playing it anymore since it's from the 2005 era.
But even if you don't use it, you might find it interesting for ideas for your own system.

https://www.rpgcrossing.com/attachment.php?attachmentid=33977

The cleanest and most functional rules light d20 system I've ever used is ICRPG.  I know, I know... I talk about it enough you'd think I have stock in Runehammer...

First, it's a recognizable d20 system.  6 stats and a check is d20 + stat + bonuses.  Most of the conditions from D&D are present too.

There are no skills or classes.  Equipment (called loot in the book) gives you bonuses for skill checks and a PC has 10 slots for active loot and 10 storage slots.  A lock pick set gives you the ability to pick locks and can give you a bonus based on the quality of that pick set.  Loot and it's bonuses can be logical an somewhat realistic or they can be silly like a rubber duck that lets you headbutt trees for gold coins.  Mundane items that don't direct game mechanical functions or that everyone would have can just be hand waived and not take up a slot.  For me it's things like note books and pens or keys.  Spells are also loot, usually in the form of a spell book.

There's no levels.  PC development is done by giving access to more loot and better loot thereby making the PC stronger.  Usually a PC starts with two pieces of loot.  Also, a piece of loot can take up more than one loot slot for particularly powerful items.

Movement and combat are more coarse that the 5' squares typical of D&D.  Ranges are described as close (melee distance), near (ranged weapon distance), and far (can be seen but too far to shoot).  I usually interpret this as zones like 2d20 does.  PC movement is that you can move one range band for normal movement and two for running.  There's an alternate method of using a measuring device that is the maximum normal movement and doubled for running.  This measuring device is called a banana.

It's got some other neat innovations as well.  One that I like and have incorporated into all my games now is the idea that all tasks have completion points.  A great example is you have a stuck door and you're trying to wedge it open.  You roll a strength check and upon a success you roll an effort die to see how far you moved it.  The effort die represents whether you're doing it just with your hands (a d4) or if you're using a pry bar (a d10).  Typically, most tasks will have 10 completion points and when you hit that the job is done.  This was an easy job but one that's time consuming or complicated can be represented by a low skill check but a high completion point count where as a difficult task might be very hard but quick.

Another innovation is to just give everything in an encounter the same target number.  A moderately easy encounter can have a target number of 11.  That means that any attack or check is a DC of 11.  You can isolate a specific check as being more difficult or easier so not everything is the same number but it's great for your notes so that you're not looking up the AC of every enemy and the DC for every lock.

Coming back to your game.  You can choose loot and bonuses based on the setting and adventure.  Various pieces of camping gear and personal items may be useful for various tasks they need to do to get clues, keep safe, and ultimately get home.  Therefore, it's loot and it does what you reasonably think it will do for bonuses.  Other camping gear that you don't thing will have much bearing on the challenges can just be hand waved as the basic personal items that a camper would have.  For example, if you plan to have challenges that involve starting a fire, then items for that purpose would be loot.  A book of matches could be part of a survival kit and therefore just one aspect of a piece of loot that does +2 for all wilderness survival checks.  Or it could be a butane torch that has a +5 to igniting fires.  If you don't plan on any challenges like this, then you could just hand wave it away saying it's likely that a camper would have matches or a lighter in their pockets.

Quote from: BadApple on November 21, 2023, 12:51:02 AM
The cleanest and most functional rules light d20 system I've ever used is ICRPG.  I know, I know... I talk about it enough you'd think I have stock in Runehammer...

I like ICRPG a lot, but if memory serves it has a somewhat restrictive license, so that might be an obstacle to publishing.

I would just release it as B/X or OSE compatible. There aren't a huge amount of OSE/BX modern games, but enough that I think it's viable.

Quote from: ForgottenF on November 21, 2023, 11:03:58 PM

Quote from: BadApple on November 21, 2023, 12:51:02 AM
The cleanest and most functional rules light d20 system I've ever used is ICRPG.  I know, I know... I talk about it enough you'd think I have stock in Runehammer...

I like ICRPG a lot, but if memory serves it has a somewhat restrictive license, so that might be an obstacle to publishing.

No, it doesn't.  (Never take legal advice from a stranger on the internet; do your own research and validation.)  As long as you aren't violating his actual copyright or trade mark, you can make compatible material and distribute it as you like.  Hank already made a public statement to this effect and several people have already done so.

Quote from: JeremyR on November 21, 2023, 11:57:45 PM
I would just release it as B/X or OSE compatible. There aren't a huge amount of OSE/BX modern games, but enough that I think it's viable.

I'd love to release it as B/X or OSE compatible, but I haven't seen modern era rules for it - classes or skill based characters or the like.  I'd like to pair it with something that is recognizable.

Quote from: BadApple on November 21, 2023, 12:51:02 AM
The cleanest and most functional rules light d20 system I've ever used is ICRPG.  I know, I know... I talk about it enough you'd think I have stock in Runehammer...

I love Runehammer.  I'm a big fan of the channel and have taken some of his running the game and scenario advice from his youtube videos.  I think the creator has a great attitude.  Releasing it for ICRPG is a possibility.  I'll look into the license and see if that makes sense.  Thanks.