diff --git a/src/graphics/arrows.c b/src/graphics/arrows.c
index e7c451a..8a5b302 100644
--- a/src/graphics/arrows.c
+++ b/src/graphics/arrows.c
@@ -79,19 +79,19 @@ void arrows_write_terminations (long x, long y, long z)
                 graphics_write_color(0.3f, 0.3f, 0.3f);
                 graphics_write_color(0.3f, 0.3f, 0.3f);
 
-                //  X - X  (EAST - WEST) axis - arrows tips
+                //  X - X  (EAST - WEST) axis - arrows tips  (red - green)
                 graphics_write_vertex (vx + (1 / max) - arrow_tip_padding, vy, vz);
                 graphics_write_vertex (vx - (1 / max) + arrow_tip_padding, vy, vz);
                 graphics_write_color(1.0f - nuance / 3, 0.0f + nuance, 0.0f + nuance);
                 graphics_write_color(0.0f + nuance, 1.0f - nuance, 1.0f - nuance);
 
-                //  Y - Y  (ZENITH - NADIR) axis - arrows tips
+                //  Y - Y  (ZENITH - NADIR) axis - arrows tips  (cyan - magenta)
                 graphics_write_vertex (vx, vy + (1 / max) - arrow_tip_padding, vz);
                 graphics_write_vertex (vx, vy - (1 / max) + arrow_tip_padding, vz);
                 graphics_write_color(0.0f + nuance, 1.0f - nuance / 3, 0.0f + nuance);
                 graphics_write_color(1.0f - nuance, 0.0f + nuance, 1.0f - nuance);
 
-                //  Z - Z  (NORTH - SOUTH) axis - arrows tips
+                //  Z - Z  (NORTH - SOUTH) axis - arrows tips  (blue - yellow)
                 graphics_write_vertex (vx, vy, vz + (1 / max) - arrow_tip_padding);
                 graphics_write_vertex (vx, vy, vz - (1 / max) + arrow_tip_padding);
                 graphics_write_color(0.0f + nuance, 0.0f + nuance, 1.0f - nuance / 4);
diff --git a/src/graphics/graphics.c b/src/graphics/graphics.c
index 074ba00..02874d7 100644
--- a/src/graphics/graphics.c
+++ b/src/graphics/graphics.c
@@ -643,7 +643,7 @@ static void show_buffers_states(int space_X, int space_Y, int space_Z, int arrow
            (arrows_nb * 14 - (buffer_lines_size - buffer_lines_size_after_cubes)) / arrows_nb, arrows_nb);
 
     if (arrows_nb > 1)
-        printf("\n     WARNING  In this test, it may happens that arrows with different weights are drawn superimposed (check the list).\n");
+        printf("\n     WARNING  In this test, it may happens that some arrows (whatever their weights) are drawn superimposed (check the list).\n");
 }
 
 
@@ -880,13 +880,15 @@ void main_test_graphics (void)
                                 // xyz,  0,   x, y, z,  xy, xz, yz,  xyz
     GLuint arrows[arrows_nb * 5];
     show_user_choices(arrows, arrows_nb, space_X, space_Y, space_Z, pref_show_grids, 1, 0);
+
+    //  WARNING  arrows with same address will be drawn superimposed
     if (arrows_nb > 0)
         for (int i = 0; i < arrows_nb; i ++) {
             arrows[i * 5 + 0] = 1 + rand() % arbitrary; //    load / weight
-            arrows[i * 5 + 1] = rand() % 6;  //    site
-            arrows[i * 5 + 2] = rand() % space_X;  //    x
-            arrows[i * 5 + 3] = rand() % space_Y;  //    y
-            arrows[i * 5 + 4] = rand() % space_Z;  //    z
+            arrows[i * 5 + 1] = rand() % 6;             //    site
+            arrows[i * 5 + 2] = rand() % space_X;       //    x
+            arrows[i * 5 + 3] = rand() % space_Y;       //    y
+            arrows[i * 5 + 4] = rand() % space_Z;       //    z
         };
 
     //  forget the next two lines during the random tests
@@ -913,12 +915,11 @@ void main_test_graphics (void)
         arrows_nb = set_arrow (arrows, arrows_nb,
                                rand() % arbitrary,  //    load / weight
                                rand() % 6,          //    site,
-                               MIN (rand() % space_X, space_X - 1),    //    x    TODO
-                                // Qu'est-ce que c'est que ce truc pas net !...
-                               MIN (rand() % space_Y, space_Y - 1),    //    y
-                               MIN (rand() % space_Z, space_Z - 1));   //    z
+                               rand() % space_X,    //    x
+                               rand() % space_Y,    //    y
+                               rand() % space_Z);   //    z
 
-    //  ligne suivante inutile:  <  ce sont les sous-fonctions de set_arrow() qui le font
+    //  ligne suivante inutile:  <  ce sont les sous-fonctions de set_arrow() qui appellent
     //  show_user_choices(arrows, arrows_nb, space_X, space_Y, space_Z, pref_show_grids, 1, 1);
 
     int weight = 0, site = 0,