Iguana vs Snakes

(Published on 28. June 2026, 10:03 by AaronH)

This puzzle was inspired and created for the Monthly puzzle prompt for June 2026 over on the CTC discord - Happy 100th birthday Sir David Attenborough.
The prompt caused me to recall the greatest chase scene in cinema history: Iguana vs Snakes from Planet Earth II.
If you are ever finding a puzzle difficult, please remember that, with the persistence of this little iguana, it is possible to survive.

Solve in SudokuPad

“Another hatchling has its first glimpse of a dangerous world. And now the snakes are on the alert. This is the best feeding opportunity they will get all year.”

An iguana hatches from a green egg and is immediately pursued by hungry snakes. Progress along each path represents the passage of time as the chase unfolds. Whenever the snake catches up, the two paths meet at the same point in their journey. The young iguana is caught, but only briefly. It escapes, leaps over a hole that ends the snake's pursuit, and reaches the safety of its own kind.

Rules

Normal sudoku rules apply: fill the grid with digits 1-9 so that no digit repeats in any row, column, or 3×3 box.
Pathfinder: Discover two paths through the grid, one each for the iguana and the snake. The iguana path is a valid German whisper and the snake is a valid modular line. Paths may move orthogonally or diagonally. Paths may not occupy rock cells or cross rock boundaries. Neither path may cross itself at all. However, the snake can cross the path of the iguana, but the path may never overlap for more than a single cell at a time. The snake is always in pursuit. Consequently, whenever the paths intersect, the snake cannot be ahead of the iguana. The snake's journey ends when it reaches the hole. The iguana's journey end upon entering row 1.
- Snake Line (Modular): Any three adjacent digits must include one digit from each of the modulo‑3 sets {1,4,7}, {2,5,8}, and {3,6,9}.
- Iguana Line (German Whisper): Adjacent digits differ by at least 5.
Fog of War: The grid is partially covered with fog. Placing correct digits will clear fog from the cell and the cells immediately surrounding. No guessing is required.
Iguana eggs: Different coloured eggs are located on the grid between two cells and represent relationships between the digits as follows:
- White eggs join adjacent digits that are consecutive.
- Black eggs join adjacent digits where one is double the other.
- Green eggs join adjacent digits that differ by 5.
- Red eggs join adjacent digits where one is odd and the other is even.
- Yellow eggs join adjacent digits that are not consecutive.