diff --git a/simu/src/main.rs b/simu/src/main.rs
index 9a4feb0..e2c7db1 100644
--- a/simu/src/main.rs
+++ b/simu/src/main.rs
@@ -261,6 +261,7 @@ impl<'a> ApplicationHandler for App<'a> {
                 let now = Instant::now();
                 if next < now {
                     next = now + Duration::from_secs_f64(1. / 30.);
+                    println!("Warning: rendering is lagging!")
                 }
                 event_loop.set_control_flow(winit::event_loop::ControlFlow::WaitUntil(next));
                 if let Some(w) = self.w.as_ref() {