diff --git a/00.brainstorming-pedagogical-teams/45.synthesis-structuring/instructions-for-levels/30.beyond/annex.es.md b/00.brainstorming-pedagogical-teams/45.synthesis-structuring/instructions-for-levels/30.beyond/annex.es.md
index d318af371..c0142fde4 100644
--- a/00.brainstorming-pedagogical-teams/45.synthesis-structuring/instructions-for-levels/30.beyond/annex.es.md
+++ b/00.brainstorming-pedagogical-teams/45.synthesis-structuring/instructions-for-levels/30.beyond/annex.es.md
@@ -214,6 +214,27 @@ Se ofrecen las siguientes categorías, pero para discusión, todas las ideas son
 !
 ! *Discovery time : 30 minutes*<br>
 ! *Resolution time : 10 minutes*
+
+! <details markdown=1>
+! <summary>
+! I choose it
+! </summary>
+! A lensball is a simple physical system: a sphere of glass of refractive index $`n=1.5`$ and of radius $`R=5\;cm`$.
+!
+! A ball lensball is placed in front of a painting. Depending on the position of the observer or the camera, 
+! the optical system (the sequence of simple optical elements crossed by light between the physical object
+! and the observed image) that forms the image differs.
+!
+! Observe the 3 images of the painting given by the lensball :
+!
+! Image 1
+!
+! ![](lentille-boule-1-transparence_L650.jpg)
+!
+! Images 2 (the smallest) and 3
+!
+! ![](lentille-boule-2-reflexions_L650.jpg)
+! </detais>
 !
 ! <details>
 ! <summary>