diff --git a/sketch.js b/sketch.js
index 75eafd4..69cfa08 100644
--- a/sketch.js
+++ b/sketch.js
@@ -78,6 +78,7 @@ function draw() {
   const polytope_is_slow = physics && particles.length > 40 || particles.length > 120;
   const polytope_if_fast = polytope && !polytope_is_slow;
   if (physics) {
+    if (!polytope_if_fast) faces = [];
     move_particles(particles, 8e-4);
   }