Compute board-game score from regions

You are given a 2D board for a board game. Each cell is encoded like G1 or W0:

• The first character is the terrain/area type (e.g., G , W , S ).
• The digit is the number of crowns in that cell (0–9).

Two cells belong to the same area/region if they have the same terrain type and are connected by 4-directional adjacency (up/down/left/right).

For each region:

$\text{regionScore} = (\#\text{cells in region}) \times (\text{sum of crowns in region})$

Return the total score across all regions.

Example

Board (rows):

1. G1, G2, W0, W1, S1
2. G2, G3, W0, W1, S1
3. S2, S3, S1, G1, S1
4. G1, G2, W0, W1, S1
5. G1, G2, W0, W1, S1

Compute the total score for this board.

Additional requirement

Write a small set of self-contained test cases that cover edge cases (e.g., all same terrain, all crowns 0, single-cell regions, multiple disjoint regions of same terrain type).