Solution to Challenge 3

Counting
Using the script with n = 6: twists = (6 // 2) ** 2 = 9, grid lines = 2 * (6 - 1) = 10.
So a 6 by 6 grid holds 9 twists.

Building
1. Pre-crease the 6 by 6 grid.
2. Add the diagonals and set mountains and valleys from your map.
3. Collapse all the twists together, working across the sheet.

Why neighbours alternate
Neighbouring twists share an edge. If both rotated the same way, the shared paper would be pulled in opposite directions and could not lie flat. Alternating the direction in a chessboard pattern lets the shared edges fold neatly.

Checkpoint: nine matching twists, a flat sheet, and an even pattern when held to the light.