diff --git a/howto-build-map.md b/howto-build-map.md
index 9acd0ce..3e9ff89 100644
--- a/howto-build-map.md
+++ b/howto-build-map.md
@@ -28,4 +28,5 @@ Now, the tile layers:
 * hiddenWalls: These wall tiles will be rendered over the relevant hiddenRoom. If these weren't here, the hidden area would just be black, possibly giving players a very good indication that a hidden area is located there.
 * hiddenTiles: Exactly like hiddenWalls, except for tiles.
 * walls: A wall tile is any tile that causes the player to collide. It doesn't have to be a wall or even a tree. It could be a regular ground tile too. Just remember that placing a tile in this layer would cause the player to not be able to walk there.
-* 
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+* doodads: This layer does not cause collisions and is rendered brighter than the tile layer.
+* tiles: Regular tiles that don't collide and are rendered fairly dim. Use this for all ground tiles like carpets, grass, dirt and water.
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