The four groups
Browser security response headers
CSP · HSTS · X-FRAME-OPTIONS · REFERRER-POLICY
Password-hashing algorithms
BCRYPT · ARGON2 · SCRYPT · PBKDF2
Block-cipher modes
ECB · CBC · GCM · CTR
Words paired with CHAIN
BLOCK · KEY · TOOL · FOOD
Why this puzzle works
The infosec puzzle. BLOCK is the murder weapon — it could belong with the cipher modes (which are block-cipher modes!) but it's the wordplay tile. CTR wants to be 'counter' the wordplay too, but it's the real abbreviation for the cipher mode. Trust the cipher-mode group has exactly the four it should. Difficulty-4: every other category here demands specialist knowledge — bcrypt vs argon2 is a real password-storage debate, GCM vs CBC is the AEAD-vs-padding-oracle debate, etc.
How to read a Connectle without solving it
A code-themed grouping puzzle rewards counting as much as recognition. Start by listing every plausible group, then notice which tiles appear in two lists. Whichever group has exactly four unambiguous members is your anchor — solve it first and the rest of the board collapses by elimination. The hardest tier (purple) is almost always wordplay: tiles that share a prefix or suffix, not a concept. If a tile feels orphaned, ask whether the same word could follow or precede a common engineering word like root, stack, cache, or queue.