# Re-Venn-ge of the Connecting Wall

An entry in Fortnightly Topic Challenge #42: Wordless Connecting Walls

Today I created a puzzle (for which a solver would need to partition 16 items into 4 connected groups of 4, and then identify a 17th item that satisfies all four connections), but - would you believe it?! - I've forgotten all of the items in it! I have a hazy recollection of the connections behind the four groups, and I've found this helpful four-way Venn diagram that I made as an aid to constructing the puzzle... but I'm stumped!

Can you help me?

Colourblind-friendly version available here.

Clues to the 4 categories:

1. One of the connecting categories relates to - one game in particular, in fact...
2. Another category relates to web development.
3. Yet another category relates to ... or is it ... Hang on, maybe ? Argh, it's one of them, I know!
4. The fourth category... Oh, I know I really should remember this! It's something I learned when I was a child, I'm pretty sure...

TASK: Use the clues and the 4-way Venn diagram to solve this puzzle backwards! Pinpoint the 4 connecting categories, identify the 16 items that made up the intended connecting wall for my puzzle, and tell me which additional item (marked by the white question marks on black in the diagram) links all 4 categories...

Hint:

2b. Wait, I remember that by 'web development' I specifically mean it has a connection to HTML...

• Holy crap this is amazing. Commented Nov 11, 2020 at 20:51
• How many brains do you have?
– PDT
Commented Nov 11, 2020 at 23:47
• What do the 3 black 'X's in the Venn diagram and the 6 black 'X's outside the Venn diagram represent? Or is that something we need to figure out ourselves? Commented Nov 12, 2020 at 0:18
• @Alaiko That's part of the puzzle! :)
– Stiv
Commented Nov 12, 2020 at 7:11
• I don't think I'm making any progress so I'll just share my one idea (rot13): Gurer ner 26 gbgny flzobyf: 17 vaibyirq jvgu gur pbaarpg jnyy naq 9 Kf. V'z thrffvat gung gurfr ercerfrag yrggref bs gur nycunorg. Gung vf, rnpu bs gur 20 jbeqf va gur iraa qvntenz fgnegf jvgu n qvssrerag yrggre, jvgu 6 yrggref hahfrq.
– JS1
Commented Nov 13, 2020 at 0:00

The groups are

1. Letters worth 1 in Scrabble (yellow): E, L, N, T
2. One-letter HTML tags (red): A, B, S, U
4. Abbeviations of rainbow colours (blue): G, O, R, Y
3. Letters used in Roman numerals (green): C, D, M, X

The answer fitting all categories is

I, which is worth 1 in Scrabble, indicates Italic text in HTML, is an abbreviation of indigo, and is the Roman numeral 1.

Filled-out Venn diagram:

• Perfect! Exactly right - great work :) I cannot describe how long it took to find 4 'reasonably findable' categories in this way so that if presented with the 16 wall items it could be uniquely resolved into 4 groups. I really wanted to include rot13(1-yrggre Crevbqvp Gnoyr flzobyf) somehow but since it was quite a large group it ended up with many, many overlaps and multiple ways to categorise the 16 items...
– Stiv
Commented Nov 13, 2020 at 9:24
• I just realised that this diagram is actually a useful tool for solving connect walls!
– PDT
Commented Nov 13, 2020 at 9:38
• Nice job! I was completely stuck with group 2. Commented Nov 13, 2020 at 10:05