Background
Last week, Brandan came up with a grid-deduction genre about filling a 6x6 grid with polystrips of lengths 1 through 8, using each length exactly once. A polystrip cannot bend twice in a row to cover a 2x2 region. The clues are given as endpoints of the strips, 15 in total. In the original version, the endpoints were marked with symbols so that each pair of identical symbols indicates a strip (one symbol given only once indicates a monomino):
. . . . A B
A C . . . .
D E F . . .
. . . F . .
. D . E C .
G H H B . .
In an answer, I proposed a variation where two kinds of symbols are given so that each strip connects from A to B (there are one more As than Bs; one of the As indicates a monomino):
A A A B . A
A B . . B A
. . B . . .
. B . . . .
. B . A . .
. . . A B .
Then in one of the comments, Dmitry Kamenetsky asked:
What happens when you replace A and B with just a single character X? So you need to join X to X. Does that still have a unique solution? An interesting puzzle in itself is to find one arrangement of X that DOES have a unique solution.
And I did find one. Now it's your turn.
Challenge
Construct a "Fifteen Crosses" puzzle that has a unique solution. Rules of the puzzle:
- A 6x6 grid is given. Fifteen cells are marked with an X.
- Use polystrips of lengths 1, 2, ..., 8 exactly once each to cover the 6x6 grid. All Xs must be at the endpoint of one of the strips. Polystrips cannot bend twice in a row to cover a 2x2 region.