A stem cell's each candidate maps to an ALS "petal"; the common candidate across all petals is eliminated from cells seeing all petals.
A "stem" cell has multiple candidates; each candidate connects to a different ALS "petal". Whichever value the stem takes, the corresponding petal activates. If all petals share a common candidate Z, any cell seeing all petals can have Z eliminated.
A generalization of ALS-XZ; very rare in practice.
23456 | 256 | 8 | 35 | 14 | 9 | 1257 | 24 | 67 |
| 1 | 259 | 3459 | 35 | 6 | 7 | 259 | 248 | 89 |
456 | 7 | 4569 | 2 | 14 | 8 | 159 | 3 | 69 |
25 | 259 | 1 | 8 | 7 | 3 | 29 | 6 | 4 |
347 | 8 | 34 | 6 | 9 | 2 | 37 | 1 | 5 |
2367 | 269 | 369 | 1 | 5 | 4 | 2379 | 28 | 789 |
56 | 3 | 56 | 7 | 8 | 1 | 4 | 9 | 2 |
| 8 | 4 | 2 | 9 | 3 | 5 | 6 | 7 | 1 |
| 9 | 1 | 7 | 4 | 2 | 6 | 8 | 5 | 3 |
This 9×9 puzzle is solver-verified to require this technique on its solution path.