Add README and revise distance metricHEADmaster

Added many inline comments for clarity.
Introduced initial version of README with gameplay details, controls, and AI logic.
Replaced Euclidean distance with Manhattan distance in standard_distance() to better
match grid-based movement without diagonal traversal.

1 files changed, 6 insertions, 0 deletions

diff --git a/field.h b/field.h
index 728d75a..7bce8c5 100644
--- a/field.h
+++ b/field.h
@@ -16,6 +16,12 @@ enum intersection_type {
     one_path     = '1',
     two_paths    = '2',
     three_paths  = '3',
+    /*
+     * Yellow blocks': ghosts can't go up from these tiles during normal
+     * movement. When entering from left or right, they can only continue
+     * straight. This restriction is ignored in frightened mode or during
+     * mode transitions.
+     */
     yellow_block = 'y',
     direct_path
 };