I started designing a new roleplaying system in September 2016, as I wanted an alternative to Savage Worlds. Initially, I had two very different ideas for how the system should work. One of those ideas evolved into Swift d12, and I still have major plans for that system, but it's turning into a rather bigger project than I'd originally envisioned. The second idea was a much lighter system, and it had the working title "Small Worlds".
Small Worlds
Drawing inspiration from Frank Turfler's Savage Dungeons project, Small Worlds was designed to have a similar look-and-feel to Savage Worlds, and even be compatible with its statblocks, so that people could use it with the many free One Sheets adventures that are available online. I revisited the concept again after the ENnies, when there was some discussion about the definition of "game" -- I wondered if it would be viable to include a 2-3 page alternative mini system in the back of a Savage Worlds setting book, so that it could technically be played as a standalone product.
Small Worlds needed dice-based attributes, but I wanted to avoid exploding dice, as I don't like the effect they have on the probabilities at certain Target Numbers. However without exploding dice, it would be impossible for a d4 to ever succeed at TN 5+, or d6 to succeed at TN 7+, etc. Thus I decided to have the player roll their attribute dice and difficulty dice at the same time, and compare them.
However, the dice mechanics didn't really feel right. They worked, but they felt fiddly and overly complex compared to the simplicity of the rest of the system, and it also felt unintuitive for the player to roll the difficulty dice themselves. You can view the system here if you're curious.
Tricube Tales
Last year I designed a minimalist RPG called Blood & Bile, which uses 1-3d6 for trait checks. I like the dice mechanics, but the problem is they require color-coded dice, which seems to be a major turnoff for a lot of people (I guess not everyone has sufficient dice of specific colors). I tried to think of ways to remove the need for colored dice, but I came up blank.
Then I picked up Tiny Dungeon, while it was Deal of the Day on DriveThruRPG. Tiny Dungeon also uses 1-3d6, but as an Advantage/Disadvantage mechanic (conceptually much like D&D 5e, The Black Hack, etc) -- so players roll 2d6 for most tests, 3d6 if they have the advantage, or 1d6 if they're at a disadvantage. It's a simple and intuitive solution, so I shamelessly pinched it.
Once I'd dropped the stepped dice mechanics from Small Worlds, the only thing it had in common with Savage Worlds was the terminology, so I changed that too, tightened up the rules, and named the new system "Tricube Tales". Eli Kurtz ran the first playtest last week, and feedback was pretty positive.
You can get the current version here: Tricube Tales
I'm still trying to decide what to do with it. I think it might be worth pairing it with a simple setting, as that would provide the reader with some working examples of how to build characters and resolve challenges. Another possibility might be to include some guidelines for applying the rules to different genres. Or maybe I'll just release it as a simple "One Sheet" system.