The completed original puzzle has nine blank white cells, nine blocked cells and three clues. Entering A at row1 column3 affects both STAR and ART; entering T at row3 column3 affects both ART and TREE. Clue selection changes navigation, while explicit Check distinguishes incomplete, wrong and correct answers.
Define the original mask and separate key
NASA's archived ISTP games page includes clue-based crosswords, offering historical context for the artifact type. The archive warns that it is no longer updated and parts may not work in current browsers. This puzzle uses independently written clues and a new grid, not NASA terms, artwork, or a claim about an active tool. NASA ISTP: Archived Puzzles and Games
Use three rows and six columns. The separate developer answer-pattern rows are STAR##, ##R###, and ##TREE, where # marks a blocked cell. Learner white cells start blank; the pattern is a key, not prefilled play.
| Clue | Start, one-based row/column | Length | Original clue | Developer answer |
|---|---|---|---|---|
| 1 Across | (1,1) | 4 | A bright point seen in the night sky | STAR |
| 2 Down | (1,3) | 3 | Creative work such as drawing | ART |
| 3 Across | (3,3) | 4 | A woody plant with a trunk | TREE |
There are 18 cells: nine white and nine blocked. The three words contain 4 + 3 + 4 = 11 letter occurrences, but they share two crossings, leaving nine unique white cells.
At (1,3), A belongs to both STAR and ART. At (3,3), T belongs to both ART and TREE. Keep those memberships in the clue definitions; there is still only one editable cell value at each coordinate.
Let clue views read the shared array
Store white-cell values by row/column key, initially empty. Define each clue as an ordered list of those keys. 1 Across reads (1,1) through (1,4); 2 Down reads (1,3), (2,3), (3,3); 3 Across reads (3,3) through (3,6).
Editing (1,3) updates the same value both linked clues read. Do not maintain separate editable strings for STAR and ART and later try to decide which one wins. A clue preview is derived output, not another source of truth.
Switching from Across to Down preserves answers and selects the appropriate cells/direction. Label the active clue and cell. The visible clue number and row/column let someone navigate the structure without relying only on highlighting.
Check explicitly and invalidate affected feedback
Check compares nonblank current clue letters with the separate developer key. A partial answer is incomplete, not a completed clue. The activity is complete only when all three clues are correct and all nine canonical cells agree with the key.
| Try this edit | What changes |
|---|---|
| Enter A at (1,3) | Both 1 Across and 2 Down read A there |
| Enter T at (3,3) | Both 2 Down and 3 Across read T there |
| Put a wrong letter at a crossing | Both linked clue comparisons reflect that error |
| Erase a crossing | Both linked clue views become partial at that position |
| Change a checked letter | Clear affected stale correctness/completion feedback |
| Reset | Nine values empty; mask and three clues preserved |
Repeated checking does not create more correct clues or count the crossing twice. A clue selection does not complete an answer. Keep wrong, incomplete, and not-yet-checked feedback distinct so the reader can see what Check established.
Reset also clears active selection and previous check messages. Restore useful focus to the first white cell or a clearly labeled start control, with no stale completed status. Keep the maintained printable learner copy free of the key; a developer key in client-side source is inspectable, not a protected teacher area.
Use the input controls
Enter one ASCII letter in a white cell. Lowercase becomes uppercase, erasure clears the shared value, and a completed multi-letter or unsupported edit is rejected as a whole. Composition waits until its end before validation; actual IME combinations still require browser review. Clue buttons select a direction, and Previous/Next move through that clue's ordered cells. Focused arrow keys move to the next white cell in the indicated grid direction without writing a letter.
The current clue preview uses underscores for empty values. After any edit, the old correctness message is cleared. Check after changing a crossing to see both affected clue results, then Reset to return to nine blanks without changing the mask.
Copy a prompt for this example
Create a complete HTML crossword with this original three-row, six-column key. A # marks a blocked square:
STAR##
##R###
##TREE
Begin with all nine white cells blank. Include these clues: 1 Across starts at row 1 column 1, has four letters, and asks for a bright point in the night sky: STAR. 2 Down starts at row 1 column 3, has three letters, and asks for creative work such as a drawing: ART. 3 Across starts at row 3 column 3, has four letters, and asks for a woody plant with a trunk: TREE.
Store one value per coordinate. The A at row 1 column 3 and T at row 3 column 3 belong to both crossing clues; editing either cell must update both word previews. Accept one ASCII letter or a blank, convert lowercase to uppercase, and reject a completed multi-letter or unsupported edit while preserving its previous value. Wait until composition ends before validating its committed text. Leave arrow keys to an active composition instead of moving grid focus.
Provide clue buttons, Previous and Next within the selected clue, arrow navigation between white cells, Check and Reset. Choosing a clue changes direction without changing letters. Check reports each clue as incomplete, wrong or correct; show completion only when all three match. Editing clears old check results. Reset clears nine values and restores useful focus while retaining the mask and clues. Use large readable cells and labeled controls that fit a phone. Return one self-contained HTML file; its answer key is inspectable client code.
For a shared-cell code walkthrough, NOS can display this prepared HTML crossword. Edit row1 column3, inspect both linked clue previews, and keep the source and separate developer key with your native puzzle files.