2D4 & Explore is a sequel to D12 & Delve.

I started with "D24 & Explore". Since most people don't own a 24-sided die (neither do I), I plan to include a table for converting D4 & D6 to D24 (as a supplement so it doesn't inflate my word count). To do so, one times the number on D4 by six (treating 4 as 0), and add the number on the D6. However, I realise that the number of the D4 is the only number that matters, and it seems a bit pointless to be rolling the D6. At that stage, I was going to make "D24 & Explore" and "D4 & Explore" as a 2-in-1 deal, changing only the target numbers and modifiers.

"D4 & Explore" would have a target number of 3+, a 50% chance to succeed without extra help and a 75% chance to succeed with proficiency and a +1 modifier. (The targe number for "D24 & Explore" would be 13+, and a +6 modifier if the character is proficient. Thus sharing the same probabilities.) I actually like designing my games with a base chance to succeed at 50%+, as failing rolls are generally less fun than succeeding. Thus, "D4 & Explore" fits my design habit quite well.

"D4 & Explore" became the actual game I was designing, and "D24 & Explore" is just a gimmick attached to it. I still wanted 24 to be a core motif for the game, so I decided to change it to 2D4 instead. With 2D4, a target of 5+ has a 62.5% chance to succeed, and a targe of 6+ has a 37.5% to succeed. At first, I was inclined to choose 5+ as the target, but once you add a +1 modifier, the chance goes up to 81.25%. Thus, the chance to fail with a modifier is 18.75%, and the chance to fail with a reroll is 3.5%. Choosing 6+ as the target number means 62.5% chance to succeed with proficiency, and around 86% to succeed with both proficiency and an item charge.

Overall, I prefer diceless mechanics that doesn't have a binary success/failure state, but since I am writing a system with dice, there should be a risk of failure when a player rolls.

For "D12 & Delve", I had the 12-word mechanics as a standalone game, and only added other parts (such as the character creation rules) to the game later. That's because (other than rolling a die) the only thing you need is to check whether a character is proficient in something or not. It is something that can be done without a character sheet. Everyone is (hopefully) good at something they do, and it is a simple concept.

For "2D4 & Explore", once I added the rule to reroll by expending a charge, I needed to explain what a charge is. To do so, I included CharGen in this game, and have every character start with 3 charges on their items.

Since "D12 & Delve" is a fantasy game, I thought of making "2D4 & Explore" a strictly sci-fi game at first. However, there is already a popular rules-lite sci-fi TTRPG with "24" in the title, so I made "2D4 & Explore" a game for speculative fiction, which basically means it is for any setting. After the 24 word RPG Jam is over, I might write a short scenario that is neither fantasy nor sci-fi, with some quirky pre-generated player characters.