diff --git a/worldgen-c/include/worldgen.h b/worldgen-c/include/worldgen.h
index 00d1a66..2b65b2b 100644
--- a/worldgen-c/include/worldgen.h
+++ b/worldgen-c/include/worldgen.h
@@ -72,9 +72,12 @@ typedef struct {
 	struct trail_segment *trail_segments;
 	size_t trail_segment_count;
 	size_t trail_segment_cap;
+	int prepass_done;
+	int prepass_min_x, prepass_max_x, prepass_min_z, prepass_max_z;
 } worldgen_ctx;
 
 void worldgen_init(worldgen_ctx *ctx, int world_seed, int sea_level, int snow_line);
 void worldgen_generate_chunk(worldgen_ctx *ctx, int chunk_x, int chunk_z, chunk_data *out);
+void worldgen_prepass(worldgen_ctx *ctx, int min_x, int max_x, int min_z, int max_z);
 
 #endif
diff --git a/worldgen-c/src/worldgen.c b/worldgen-c/src/worldgen.c
index a75a135..1d8d29b 100644
--- a/worldgen-c/src/worldgen.c
+++ b/worldgen-c/src/worldgen.c
@@ -130,6 +130,7 @@ static void generate_chunk_trails(worldgen_ctx *ctx, int chunk_x, int chunk_z, c
 static void generate_chunk_grass(worldgen_ctx *ctx, int chunk_x, int chunk_z, column_data columns[CHUNK_SIZE][CHUNK_SIZE], chunk_data *out);
 static void generate_chunk_flowers(worldgen_ctx *ctx, int chunk_x, int chunk_z, column_data columns[CHUNK_SIZE][CHUNK_SIZE], chunk_data *out);
 static void generate_chunk_cabins(worldgen_ctx *ctx, int chunk_x, int chunk_z, column_data columns[CHUNK_SIZE][CHUNK_SIZE], chunk_data *out);
+static void ensure_trail_prepass(worldgen_ctx *ctx, int chunk_x, int chunk_z);
 static void trail_node_position(worldgen_ctx *ctx, int node_x, int node_z, double spacing, double *out_x, double *out_z);
 static void carve_trail_pad(worldgen_ctx *ctx, int chunk_x, int chunk_z, chunk_data *out, column_data columns[CHUNK_SIZE][CHUNK_SIZE], int center_x, int center_z, int radius, int target_height);
 static void carve_trail_span(worldgen_ctx *ctx, int chunk_x, int chunk_z, chunk_data *out, column_data columns[CHUNK_SIZE][CHUNK_SIZE], int x0, int z0, int x1, int z1, int width);
@@ -154,6 +155,30 @@ static uint32_t hash_coords3(int x, int y, int z, uint32_t seed) {
 	return h ^ (h >> 16);
 }
 
+static double land_value(worldgen_ctx *ctx, int x, int z) {
+	column_data col = get_column_data(ctx, x, z);
+	double value = 0.0;
+	double ore_bonus = 0.0;
+	for (int y = 1; y < col.height - 3; y += 6) {
+		if (generate_coal(ctx, x, y, z, col.height, col.biome)) {
+			ore_bonus += 0.08;
+		}
+		uint16_t ore = generate_normal_ores(ctx, x, y, z, &col);
+		if (ore != BLOCK_STONE) ore_bonus += 0.05;
+	}
+	value += ore_bonus;
+	if (col.biome == BIOME_OLD_GROWTH_PLAINS) value += 0.2;
+	if (col.biome == BIOME_WEST_KY_COALFIELDS) value += 0.1;
+	if (col.has_water && col.height >= col.water_surface - 2 && col.height <= col.water_surface + 2) {
+		value += 0.12;
+	}
+	int slope = ground_slope(ctx, x, z);
+	value -= clamp01((double)slope / 6.0) * 0.15;
+	double noise = simplex_noise2(&ctx->noise, x * 0.0015, z * 0.0015) * 0.5 + 0.5;
+	value += (noise - 0.5) * 0.08;
+	return value;
+}
+
 static void set_block_with_height(chunk_data *chunk, int local_x, int local_z, int y, uint16_t id) {
 	if (local_x < 0 || local_x >= CHUNK_SIZE || local_z < 0 || local_z >= CHUNK_SIZE) return;
 	if (y < 0 || y >= CHUNK_HEIGHT) return;
@@ -2659,6 +2684,9 @@ void worldgen_init(worldgen_ctx *ctx, int world_seed, int sea_level, int snow_li
 	ctx->trail_segments = NULL;
 	ctx->trail_segment_count = 0;
 	ctx->trail_segment_cap = 0;
+	ctx->prepass_done = 0;
+	ctx->prepass_min_x = ctx->prepass_max_x = 0;
+	ctx->prepass_min_z = ctx->prepass_max_z = 0;
 	simplex_init(&ctx->noise, (uint32_t)world_seed);
 }