diff --git a/src/javascript/simulations/doubleSlit.js b/src/javascript/simulations/doubleSlit.js
index a6a9c1b..3c6f626 100644
--- a/src/javascript/simulations/doubleSlit.js
+++ b/src/javascript/simulations/doubleSlit.js
@@ -165,7 +165,9 @@ class DoubleSlitSimulation extends Simulation {
     mouseUp = (event) => {};
 
     mouseMove = (event, x, y) => {
+        const prevX = this.screen.x;
         this.screen.x = Math.max(Math.min(x, this.screen.maxX), this.screen.minX);
+        if (prevX === this.screen.x) return;
         this.redraw = true;
         this.cache = {};
     }
diff --git a/src/javascript/simulations/nSlit.js b/src/javascript/simulations/nSlit.js
index 67ea08e..451d6c0 100644
--- a/src/javascript/simulations/nSlit.js
+++ b/src/javascript/simulations/nSlit.js
@@ -175,7 +175,9 @@ class NSlitSimulation extends Simulation {
     mouseUp = () => {};
 
     mouseMove = (event, x, y) => {
+        const prevY = this.screen.y;
         this.screen.y = Math.max(Math.min(y, this.screen.maxY), this.screen.minY);
+        if (prevY === this.screen.y) return;
         this.redraw = true;
         this.cache = {};
     }
diff --git a/src/javascript/simulations/singleSlit.js b/src/javascript/simulations/singleSlit.js
index 66d55a8..2ebe63f 100644
--- a/src/javascript/simulations/singleSlit.js
+++ b/src/javascript/simulations/singleSlit.js
@@ -105,7 +105,9 @@ class SingleSlitSimulation extends Simulation {
     mouseUp = (event) => {};
 
     mouseMove = (event, x, y) => {
+        const prevX = this.screen.x;
         this.screen.x = Math.max(Math.min(x, this.screen.maxX), this.screen.minX);
+        if (prevX === this.screen.x) return;
         this.redraw = true;
         this.cache = {};
     }