diff --git a/README.md b/README.md
index c9407b8..0c2c3f0 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # FDF - fil de fer
 
-**this is an exercize to discover 3D drawing, keyboard events, and pixel images manipulation**
+### this is an exercise to discover 3D drawing, keyboard events, and pixel images manipulation
 
 it reads a map, which is a simple text file like this :
 
@@ -12,7 +12,7 @@ it reads a map, which is a simple text file like this :
 0  0  0  0  0
 ```
 
-and it convert it into a rectangular net, like a landscape with the height equal to the numbers :
+and it converts it into a rectangular net, like a landscape with the height equal to the numbers :
 
 ![example 3D of map before modification](assets/fdf_demo_1.jpg)
 
@@ -20,7 +20,17 @@ we can modify the map to change the 3D drawing :
 
 ![example 3D of map after modifications](assets/fdf_demo_2.jpg)
 
-then it listen to keyboards events to transform the 3D, like turning around, zooming... :
+### it is based on a library called [minilibx](https://github.com/42Paris/minilibx-linux), which is like a simplified version of X11
+
+some of the difficulties of this program :
+
+- finding the equations to transform a 2D drawing into a perspective
+- drawing a line between two points
+- bits manipulation for colors
+- organization of the code to take care of all the events and transformations
+- building images instead of asking the minilibx library to draw each pixel one by one
+
+it can listen to keyboards events to transform the 3D, like turning around, zooming... :
 
 **zoom :**