Index: binaries/data/mods/public/maps/random/biome_demo.js
===================================================================
--- /dev/null
+++ binaries/data/mods/public/maps/random/biome_demo.js
@@ -0,0 +1,107 @@
+Engine.LoadLibrary("rmgen");
+Engine.LoadLibrary("rmgen-common");
+Engine.LoadLibrary("rmbiome");
+
+setSelectedBiome();
+
+const heightLand = 3;
+
+var g_Map = new RandomMap(heightLand, g_Terrains.mainTerrain);
+
+
+const MAP_CENTER = new Vector2D(fractionToTiles(0.5), fractionToTiles(0.5));
+
+const PATCH_SIZE = 30;
+
+const PATCH_PER_ROW = scaleByMapSize(1, 6); // * 2 + 1 in practice
+
+const Y_START = -2;
+
+Engine.SetProgress(10);
+g_Map.log("Creating terrain patches");
+
+{
+	let x = -PATCH_PER_ROW;
+	let y = Y_START;
+	for (const terrain in g_Terrains)
+	{
+		++x;
+		if (x >= PATCH_PER_ROW)
+		{
+			++y;
+			x = -PATCH_PER_ROW;
+		}
+
+		const placer = new RectPlacer(
+			new Vector2D(x * PATCH_SIZE, y * PATCH_SIZE).add(MAP_CENTER),
+			new Vector2D(x * PATCH_SIZE + PATCH_SIZE - 1, y * PATCH_SIZE + PATCH_SIZE - 1).add(MAP_CENTER)
+		);
+
+		createArea(placer, new TerrainPainter(g_Terrains[terrain]), []);
+	}
+
+	// Create a water area.
+
+	y = Y_START - 1;
+	const placer = new RectPlacer(
+		new Vector2D(0, 0),
+		new Vector2D(fractionToTiles(1), MAP_CENTER.y + Y_START * PATCH_SIZE - 1)
+	);
+
+	createArea(placer, new SmoothElevationPainter(ELEVATION_SET, -8, 12));
+
+	paintTerrainBasedOnHeight(-12, -1, 1, g_Terrains.water);
+	paintTerrainBasedOnHeight(-1, 1, 1, g_Terrains.shore);
+	paintTerrainBasedOnHeight(1, 3, 1, g_Terrains.shoreBlend);
+
+}
+
+Engine.SetProgress(40);
+g_Map.log("Creating objects.");
+
+{
+	let x = -PATCH_PER_ROW;
+	let y = Y_START;
+	for (const gaia in g_Gaia)
+	{
+		++x;
+		if (x >= PATCH_PER_ROW)
+		{
+			++y;
+			x = -PATCH_PER_ROW;
+		}
+
+		for (let xx = -1; xx <= 1; ++xx)
+			for (let yy = -1; yy <= 1; ++yy)
+				g_Map.placeEntityAnywhere(g_Gaia[gaia],
+					0,
+					new Vector2D(
+						x * PATCH_SIZE + PATCH_SIZE / 2 + xx * 4,
+						y * PATCH_SIZE + PATCH_SIZE / 2 + yy * 4
+					).add(MAP_CENTER),
+					0
+				);
+	}
+	for (const gaia in g_Decoratives)
+	{
+		++x;
+		if (x >= PATCH_PER_ROW)
+		{
+			++y;
+			x = -PATCH_PER_ROW;
+		}
+
+		for (let xx = -1; xx <= 1; ++xx)
+			for (let yy = -1; yy <= 1; ++yy)
+				g_Map.placeEntityAnywhere(g_Decoratives[gaia],
+					0,
+					new Vector2D(
+						x * PATCH_SIZE + PATCH_SIZE / 2 + xx * 4,
+						y * PATCH_SIZE + PATCH_SIZE / 2 + yy * 4
+					).add(MAP_CENTER),
+					0
+				);
+	}
+}
+
+g_Map.ExportMap();
Index: binaries/data/mods/public/maps/random/biome_demo.json
===================================================================
--- /dev/null
+++ binaries/data/mods/public/maps/random/biome_demo.json
@@ -0,0 +1,10 @@
+{
+	"settings" : {
+		"Name" : "Biome demo",
+		"Script" : "biome_demo.js",
+		"Description" : "A random map script that shows everything a biome specifies, for quick testing.",
+		"CircularMap" : true,
+		"SupportedBiomes": "generic/",
+		"Keywords": ["demo"]
+	}
+}