Been a couple interesting posts recently on the subject of rules-light systems. I think this is more a reaction to the success of trendy new “lite” systems like Murk Berg, Care’n, Laser Feelins, etc, with which I’ve not interacted heavily to be honest. It certainly behooves me to say something on the subject though, given I have published a little heartbreaker that has “light” in the tile (Pathfinding Light). I’ll try and poke a little on my thinking for it, while also addressing Noism’s and Prince’s concerns. I’d call this self-aggrandizing, but given I’m publishing this one CC and it’s for free on DriveThru, I’m at a loss for how any aggrandization would occur from this.
  My marketing copy on Pathfinding Light talks about making it a simple, light, and easy game of d20 that actually supports campaign play. Kind of a Five Torches Deep treatment, but for Pathfinder as the base rather than 5E. My motivation was to see if the chassis could support a more old-school play experience, in part, but honestly another reason for it is that I wanted to print a booklet-sized product of only twenty pages counting covers. Five sheets of paper, folded and stapled, gets me a pleasing little booklet that I’ve noticed players will actually read. I think part of the genius of Knave that actually makes sense is the writer’s awareness that the majority of players would not read a 100+ page book cover-to-cover if their lives were on the line. I tried to organize things in my booklet so that players are actually usually only hitting 2-3 pages, for that matter, and the page count includes six pages of the GM section, a sample adventure, and a character sheet template. It’s been surprisingly successful for people using it, delivering a light if not ultra-light game that actually works for campaigns.
  A lot of the criticism for the new ultra-lights is the very reasonable objection that they’re so stripped-down that you cannot use them to…actually play a game. A distressing number of “rules light” systems aren’t actually there to play with by themselves…they’re designed as a light overlay for the vast and murky tribal knowledgebase that is “D&D”. Often, they propose to add something new, but in practice they’re just linking in the pop-culture knowledgebase of Call of Cthulhu. Give Knave to a precocious-but-culturally-isolated group of five nerdy 11-year-olds, and they’re going to struggle to play with it. My biggest criticism of rules-light systems is that they’re being sold to people who have played D&D, not to who you’d think they’d be best for, an audience unfamiliar with any of the tropes or playstyles built up over the last half a century of the hobby.
  I’ve tried myself to avoid that. The very basic mechanic of the d20 system is gorgeous…

1. Players try to accomplish thing.
2. GM sets the target number to succeed at thing.
3. Player(s) roll a d20 with relevant bonus(es).
4. GM narrates success or failure.

  There’s no reason why this central mechanic cannot be used for almost everything, and I do appreciate the simplicity there. Ages-ago lost techniques like morale checks and reaction rolls can be accomplished via d20 just as easily as d6. I’d like to think that group of sixth graders could take my booklet and a dice set and play out years-long campaigns with just those. That’s ambitious, but if you aren’t at least trying for that, you don’t have a rules-light system…
  …you just have a rules supplement.

  A refrain commonly heard among RPG module reviewers is "there is no order of battle".  The complaint is typically caused by the tendency of modules to key and run dungeons with living, sentient denizens as if they were non sentient undead or automatons, just sitting in rooms or zones waiting for the party of adventurers to blunder in and have a fight. A wise order of battle acknowledges that intelligent and social monsters will react to any invasion with reinforcements, alarms, and at times even offensively. The reason for not having an order of battle is laziness...sometimes on the part of the module writer, but also sometimes because the writer might guess that the GM running the module would also be lazy about actually tracking time and movement. 
  Fortunately, we are talking about Role-Playing Games. A disciplined order of battle is something we can expect from organized and professional soldiery, but it's typically easier for the game master to do what comes most naturally...just put on the role of the opposing force's characters. The goblin king will have made plans with his lieutenants, but those plans aren't going to be strictly adhered to and the lieutenants themselves will have their own ideas about what to do. For the intelligent but typically chaotic goblins, kobolds, orcs, bandits, pirates, lizardmen, bugbears, raiders, gnolls, or other rapscallions who populate most dungeons, lairs, and fortresses in these games the thing more important than an "order of battle" is the GM deciding what orders are going to be given by panicking characters of questionable wisdom, thus think orders of battle.
  This brings us back to that other oft-neglected part of original D&D, the morale system and reaction rolls. The party arrives at the goblin-infested Keep on the Land's Border, and kills off the initial guards. One goblin flees to Lieutenant Gleebsnorp, who then has to make his own reaction roll and morale check. Does he send a runner to King Gorf the Obese? Does he attack immediately? Does he hide? This is where an otherwise linear-seeming assault can also have numerous branches. If the player characters seemed ruthless, then Lt. Gleebsnorp certainly won't consider surrender, but maybe he's more likely to cut and run. If the party advances hot on the heels of the escapee, then they get to hit the lieutenant before he has a chance to dither, maybe then he's more likely to stick to the plan. Having an order of battle is important, but giving the players real living foes is much more about them acting out choices rather than just following a script. 
  And then way when King Gorf the Obese crushes them at the gates with the entire goblin warband, they can perhaps assign more blame to themselves. On second thought, maybe they should have been a little less merciless in that initial push...