diff --git a/datas/README.md b/datas/README.md
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--- a/datas/README.md
+++ b/datas/README.md
@@ -1,4 +1,14 @@
 # statics datas
 
-Things like `height_fields` or `image_map` files...
+This directory is the home of things like :
 
+- `height_fields`, or « Champs d'altitude »
+- `image_map`, or « Papier peint »
+
+But you have to provide your homebrewed one, who must be of high
+quality, larger than 512x512 pixels. On the other side, you are
+free to experiment with ugly files *:)*
+
+You can also see the colors for the EGA conversion : 
+![16 colors](ega-16colors.png), used by this
+[script](tools/build-ega-mp4.sh).
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