diff --git a/Engine-prototype.md b/Engine-prototype.md
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--- a/Engine-prototype.md
+++ b/Engine-prototype.md
@@ -1,6 +1,14 @@
 ## Basis optimization
 
-The size of the Gröbner basis depends a lot on the variable order. So far, I've gotten the best performance with the degree › reverse lexicographic monomial order and the following variable order.
+### Best order
+
+The size of the Gröbner basis depends a lot on the variable order. For the examples below, I've gotten the best performance with the degree › reverse lexicographic monomial order and the following variable order.
 
 * First, sort by coordinate: $r$, $s$, $x$, $y$, $z$
-* Within each coordinate, put spheres before points: $r_\text{s1}, r_\text{p1}, r_\text{p2}$
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+* Within each coordinate, put spheres before points: $r_\text{s1}, r_\text{p1}, r_\text{p2}$
+
+### Test suite
+
+* One point on a sphere
+* Two points on a sphere
+* Three mutually tangent spheres
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