Word Fit (Criss-Cross)

Fit the listed words into the interlocking skeleton — no clues, just shapes and crossings.

What it is

A crossword-like frame of horizontal and vertical slots, and a word list grouped by length. Every word is used exactly once; crossing slots must agree on their shared letter. Unlike a crossword there are no definitions — the letter crossings are the whole constraint.

How to play

Start where the list gives no choice: a length with only one word, or the longest slot. Each placement fixes letters in every crossing slot, narrowing their candidate lists; the puzzle cascades from a single confident entry. When two words could fill a slot, look one crossing further — one of them will contradict a neighbour.

Purpose

The crossword’s self-contained cousin: it needs no clue-writing, so it ships in any theme instantly — which is exactly why it precedes the crossword in the product plan. In the workspace it is a clean exact-assignment search: most-constrained-slot-first over a length-bucketed bank.

History

“Kriss Kross” fill-in puzzles have run in Dell and Penny Press magazines since the mid-20th century, a genre refined for decades before ever getting a canonical inventor — none is recorded.

This implementation

• Spec knobs: rows, cols, words/theme, difficulty.
• Generation: the skeleton is generated first (a random walk of slots with intersections), then filled by backtracking with most-constrained-slot-first from a wordlist bucketed by length.
• Guarantees: the shipped arrangement is proven unique — no other assignment of the same word list fits the same skeleton — which is the property that makes an answer key honest.
• Difficulty: slot count, crossing density, and how many words share each length (more same-length words means more real choice), banded.