That’s a great question. Here are some of the big titles I’ve come across, starting now and working background.

• Robin Laws’ GUMSHOE engine stands out as an interesting way to handle investigations in RPGs. I particularly like two games that use those rules, The Esoterrorists and Trail of Cthulhu.
• There are a number of indie RPGs that I find quite interesting, such as Agon, Dungeon World, Dogs in the Vineyard, and a number of others. I like that they’re focused on a specific story or type of game played in one or two sessions. It’s a nice change of pace from games that are more focused on campaign play.
• Feng Shui’s stunt system and setting were both very interesting to me when it first came out. I’m really happy that I had the chance to work on that game. The stunt system and core mechanic are easy to pick up. I’ve had some of the best luck introducing new players to RPGs with Feng Shui.
• The same goes for Unknown Armies. In my mind, it’s the definitive modern occult horror roleplaying game. I really loved how the game’s cosmology and basic premise meshed with its system, along with its new twist on sanity mechanics.
• Warhammer FRP was the first game that showed me how a system and a setting can blend together. The career system gave your character a real sense of place in the world, and I think that’s key to immersive RPG play.
• Call of Cthulhu is my favorite non-D&D RPG. Like many of the other games on this list, it does an excellent job of immersing you in a setting through both its writing and mechanic. The sanity rule is, in my mind, one of the first and best ways to reflect the tone and feel of a genre through a game rule.

The odd thing is that these games have had wildly different influences on my approach to D&D. D&D has always been its own beast. For instance, if we took a cue from indie RPGs and made a very focused game, I think that would alienate a lot of people. Gamers like the unbounded possibilities that D&D presents to them. By the same token, if we tie a setting too tightly to the game, a lot of DMs would rebel because they see much of the fun in the game coming from building their own rules.​

There have always been a wide range of people who play D&D, so in some ways were merely addressing the range of tastes that have been with the game since the beginning. If you think of how people talk about the game – mechanics, story, creating campaigns – that’s been there since the beginning.

The first step is to get a sense of how people play D&D and what they like about the game. That’s where the playtest serves a huge role. That gives us the basic targets we need to aim at for creating the game.

The feedback also shows us where we need to be flexible. For instance, we know that while many people like the classic D&D wizard, there are also big groups that want alternative ways to play spellcasters. With that in mind, we can take some of our classes and give them mechanics and story elements that are more distinct and unique. You might not like how the wizard uses magic, but that means you can opt to play a warlock or sorcerer.​

The essence of D&D lies in the cultural elements that tie the game together across its editions. It’s things like wizards losing spells when they cast them, magic missile striking unerringly, trolls that regenerate, and so on. That’s all down in the details, but those are the kinds of things that make D&D stand out.

On top of that, there’s the big idea of D&D that players create unique characters and DMs create unique settings and adventures. That was huge in 1974, and it’s still the critical part of the game today.​

It’s funny, because based on online discussions you’d think that there were huge differences between players of different editions. However, what we’ve seen in our feedback is that people are much closer than you’d suspect.

In terms of game design, I think that 3e and 4e represent the biggest philosophical shifts. 3e was all about unifying everyone under the same set of rules. The idea was that it’s easiest for everyone if you can move from campaign to campaign without learning all sorts of new rules. 2e had embraced more optional rules, and TSR had made it clear in Dragon magazine that they expected people to play by the official rules.

4e focused on making the DM’s job easier while also making the specific experience of playing the game the same across all tables. The idea was to reduce variance in the game to make things more predictable.​

I think the difference speaks to one of the key things that people like about D&D Next. We’re definitely moving back to a more open game, where DM adjudication is more important and a DM’s individual skill plays a bigger role in how the game works. That’s a key, unique trait of RPGs that other types of games can’t duplicate. With gaming becoming more and more crowded, it’s key for us to emphasize our unique traits and strengths.

The drawback is that some DMs might feel adrift. Sometimes, it’s nice to have specific rules to fall back on. This is one area where I see modularity stepping in. I’d love to have a detailed set of rules, similar to 3e’s comprehensive approach, that DMs can opt into. You can imagine these rules almost like tournament rules, a specific set of rules more detailed than most tables need but available for DMs to use as a reference if they so choose.​

As far as I know, 4th edition was the first set of rules to look to videogames for inspiration. I wasn’t involved in the initial design meetings for the game, but I believe that MMOs played a role in how the game was shaped. I think there was a feeling that D&D needed to move into the MMO space as quickly as possible and that creating a set of MMO-conversion friendly rules would help hasten that.

What we’ve learned since then is that the specific RPG rules aren’t very useful for making other games. Instead, the world lore, feel of the game, distinct features of each class, race, and monster, and so on are much, much more important. If you look at our current boardgames, they don’t use the same exact rules as the RPG but they evoke a similar feel. That’s really the key to us. We want to be able to have a clear, easily understood definition of what a wizard or paladin is. We can then transfer that definition into other games. As long as the feel and key story beats are there, the specific rules are secondary.​

Modularity starts with a simple core. The simpler the core, the fewer the basic interactions, the easier it is to see how things work in the game. I’ll be very happy if this edition of the game is the most hackable version of the rules that we’ve released.

In terms of actual rules modules, I see them as important to allowing groups to evoke a specific feel for their campaign. That might be something like making healing less plentiful or adding more realistic injuries to evoke a grittier feel. Other groups that like miniatures play and the tactical challenges posed by combat probably want more details in the combat system.

The modularity speaks somewhat to evoking the feel of different editions, but I also think that there are a lot of different takes on the key elements of older editions. Some people like AD&D’s lethality, while others like that the rules are fairly straightforward and characters easy to manage. I think that if we tried to create a canonical set of AD&D options, many people would disagree with our take.

Instead, we give people the options that they can mix and match if they choose to create the specific campaign they want.​

When we talk about balance, we want to make sure that the character classes are roughly equivalent in effectiveness across the three basic pillars of D&D play: combat, exploration, and interaction. Some classes might be better in one area that another, but the gap is never so huge that players feel ineffective.

From a monster stand point, the key to balance is to make sure that we can give DMs clear guidance on a monster’s power level and XP value. If a DM throws an ogre at the party, the DM should have a sense of how much of a challenge that might be. We don’t really care how the DM uses these tools. A DM might want to run lots of easy fights, one big fights, or put in monsters that the PCs aren’t meant to fight. We just want the DM to have a good idea of the relative power between characters and monsters.

For modularity, the key is to let DMs know how a new rule can change the game. We trust that DMs will alter the game to fit what they and their groups want out of D&D. If we have a lethal, gritty hit point option, we’re not worried about maintaining balance across everything because the DM has opted into that. To some groups, balance is meaningless, so there’s no point in trying to enforce that in all cases.

If we keep the core simple and transparent, I believe that it will be much easier to create new content. Precise balance is really only possible through lots of playtesting, but I think that if DMs use our existing content as a guide they’ll find it easier to create new stuff.​

One of our design goals is to create a unique mechanic for every class. I’m really happy with how our new fighter mechanic turned out, and I’m also excited with how our non-cleric and wizard spellcasters are developing. My hope is that the new class mechanics are interesting, while at the same time making those classes feel more vivid and closer to their core identity than ever before.

As we solidify the base and deliver the core of D&D, I’d like to start exploring new ideas and concepts specifically in rules modules. I think there’s some exciting potential for people to take D&D in really unique, interesting directions. With modules, we don’t have to worry about anyone other than the people who want that specific option. It can be much more vivid and deep, rather than when we try to make rules that appeal to everyone.​

This goes back to the idea of having a simple core. When you start with fewer assumptions, or with basic rules that work together clearly and elegantly, it’s much easier to alter the core through modules. Part of it is also thinking ahead.

For instance, when it comes to wizards we’re adding an option to the core class to represent a wizard’s arcane tradition. For the core game, that might speak to school specialization, wild magic, the war mage, and so on. Within a setting like Dragonlance, that option list might boil down to red, black, and white robes, with each one getting a unique set of mechanics or spells.

For something like Dark Sun, we might simply allow all characters to gain psionic wild talents. We can then also turn around and give DMs the tools to create a savage, dangerous world. That’s probably as simple as telling Dark Sun DMs to use more powerful monsters and create more dangerous adventures than ones created using the standard guidelines. It might simply be an XP table that gives DMs a bigger budget for adventures and slows down character advancement. That creates a deadlier, more dangerous environment without introducing massive alterations to the rules.​