Map coordinates

The world is 80 tiles wide and 50 tiles high. Coordinates run from 0–79 and 0–49. Horizontal movement wraps; vertical movement does not. wrap_x() in PATH.C adds or subtracts 80 once, so callers must keep coordinates within one map width of the valid range. map_in_bounds() in MAP.C checks both axes.

Distance

map_dist(x1, x2, y1, y2) in CORE.C takes the shortest horizontal difference across the wrap seam. It then calls half_dist():

dx = min(abs(x1 - x2), 80 - abs(x1 - x2))
dy = abs(y1 - y2)
distance = max(dx, dy) + min(dx, dy) / 2

Division truncates. An orthogonal or diagonal neighbour is at distance 1; two diagonal steps give distance 3. This is a scoring measure, not a count of movement points. The separate distance_twice() helper returns 2 * max(dx, dy) + min(dx, dy) without the division.

Neighbours and city radius

spiral_x and spiral_y provide offsets for searches around a tile. Directions 1–8 start north and proceed clockwise. City workers use the separate radius_dx[21] and radius_dy[21] tables. Their footprint is a five-by-five square without its four corners. Tile 20 is the centre.

Display

reveal() in MAP.C draws a 15-by-12 tile viewport, with 16-by-16 pixel tiles beginning at screen position (80, 8). The left panel includes an 80-by-50 overview. Display coordinates and world coordinates are separate; map_x0 and map_y0 place the viewport on the world.