If you just pick the wider of the dimensions then you get a more even spread vs random direction.

map.cpp

@@ -130,7 +130,7 @@ inline int make_split(std::mt19937 &gen, Partition &cur, bool horiz) {
 void partition_map(std::mt19937 &gen, Partition &cur, int depth) {
   println(">>>> DEPTH: {}", depth);
   std::uniform_int_distribution<int> rsplit(0, 1);
-  bool horiz = rsplit(gen);
+  bool horiz = cur.width > cur.height ? false : true;
   int split = make_split(gen, cur, horiz);
   Partition left;
   Partition right;