diff --git a/Engine-prototype.md b/Engine-prototype.md
index 78618fa..8495497 100644
--- a/Engine-prototype.md
+++ b/Engine-prototype.md
@@ -7,7 +7,7 @@
 
 ### Challenging examples
 
-With three mutually tangent spheres, `HomotopyContinuation` doesn't seem to find solutions, even though we know there are some. One solution, in $[r, s, x, y, z]$ coordinates, is:
+With three mutually tangent spheres, `HomotopyContinuation` doesn't seem to find real solutions, even though we know there are some. One solution, in $[r, s, x, y, z]$ coordinates, is:
 * $[0, 0, 0, 0, 1]$ (plane perpendicular to $z$ axis)
 * $[1, 0, 0, 0, 1]$ (unit sphere above plane, touching at $[x, y] = [0 ,0]$)
 * $[1, 4, 0, 2, 1]$ (unit sphere above plane, touching at $[x, y] = [0, 2]$)