Исправлено #2

composeApp/src/wasmJsMain/resources/styles.css

@@ -7,5 +7,10 @@ html, body {
 }
 
 canvas {
+    position: fixed;
+    top: 0;
+    right: 0;
+    bottom: 0;
+    left: 0;
     outline: none;
 }