diff --git a/examples/ferromagnet.rs b/examples/ferromagnet.rs
index 7c144a4..8925e32 100644
--- a/examples/ferromagnet.rs
+++ b/examples/ferromagnet.rs
@@ -48,6 +48,7 @@ fn main() {
     let mut renderer = render::MultiRenderer::new()
         .with(render::Y4MRenderer::new("ferromagnet.y4m"))
         .with(render::ColorTermRenderer);
+    //let mut renderer = render::NullRenderer;
     loop {
         //let imp = match state.step_no() {
         //    20..=60 => 1e6,
@@ -70,7 +71,7 @@ fn main() {
         }
         if state.step_no() % 1 == 0 {
             renderer.render(&state);
-            thread::sleep(time::Duration::from_millis(33));
+            //thread::sleep(time::Duration::from_millis(33));
         }
         state.step();
     }
diff --git a/src/render.rs b/src/render.rs
index 805bc53..80cbc85 100644
--- a/src/render.rs
+++ b/src/render.rs
@@ -242,3 +242,8 @@ impl Renderer for MultiRenderer {
         }
     }
 }
+
+pub struct NullRenderer;
+impl Renderer for NullRenderer {
+    fn render(&mut self, state: &SimState) {}
+}