1. Nurikabe Puzzle Drew Housten

2. Terms and Notation #x - cell marked with an x Unmarked - cell that hasn’t been marked as open or closed Open - cell connected to a numbered cell Closed - cell that is filled in

3. Note Some example board segments are not valid puzzles

4. Step 1: Close cells adjacent to #1s 1 1 Unmarked Realm1 Realm2 Closed Open

5. Step 2: Close any Cell in between 2 #x’s 1 2 1 2 1212 Unmarked Realm1 Realm2 Closed Open

6. Step 3: Identify “Realms” Start with the Maximum reach 3 Unmarked Realm1 Realm2 Closed Open

7. Step 3: Identify “Realms” Remove Open and Closed cells from the realm 3 Unmarked Realm1 Realm2 Closed Open

8. Step 3: Identify “Realms” Remove Closed cells from the realm 3 Unmarked Realm1 Realm2 Closed Open

9. Step 4: Overlay all Realms 12 3 1 Unmarked Realm1 Realm2 Closed Open

10. Step 5: Close any cell not covered by at least one realm 12 3 1 Unmarked Realm1 Realm2 Closed Open

11. Step 6: Check for forced open Unmarked Realm1 Realm2 Closed Open If any realm contains exactly the number of cells as the contained number, make them all open 2 2

12. Step 7: Reduce maximum reach Unmarked Realm1 Realm2 Closed Open If an open cell is only covered by one realm, it belongs to that number. Because of this requirement, the realm will shrink to be able to connect to the open cell. Repeat step 5.

13. Step 8: Remove cells adjacent to Open Cells Unmarked Realm1 Realm2 Closed Open Any cell adjacent to an Open Cell that belongs to a different realm should be closed. Repeat step 5.

14. Step 9: Check for blocks of 3 closed Unmarked Realm1 Realm2 Closed Open A block of 3 closed forces an open

15. Step 10: Check for blocks of 2 closed Unmarked Realm1 Realm2 Closed Open A block of 2 indicates that at least one of the other 2 must be open. If the 2 unmarked are in only one realm, at least one of the 2 must be connected to that number. If one cell must be Open for the other to be, then the first cell must be Open. This will reduced the maximum reach of the realm (Step 7). If each of the unmarked cells is in only 1 realm and the realms are not the same, one of the cells must be closed