Begrenze die Anzahl der erstellten Finger auf MAX_TOUCHES und verhindere die Auswahl, wenn die maximale Anzahl erreicht ist.

js/app.js

@@ -1,6 +1,7 @@
 document.addEventListener('DOMContentLoaded', function(){
   const stage = document.getElementById('stage');
   const touches = new Map(); // id -> {el,x,y}
+  const MAX_TOUCHES = /iPhone/.test(navigator.userAgent) ? 5 : 20;
   let selecting = false;
   let selectionDone = false;
   let selectionTimer = null;
@@ -131,9 +132,12 @@ document.addEventListener('DOMContentLoaded', function(){
   stage.addEventListener('touchstart', function(e){
     e.preventDefault();
     const changed = Array.from(e.changedTouches || []);
-    changed.forEach(t=>createFinger(t));
-    cancelSelection();
-    selectionTimer = setTimeout(startSelectionIfNeeded, 700);
+    const prevSize = touches.size;
+    changed.forEach(t=>{ if(touches.size < MAX_TOUCHES) createFinger(t); });
+    if(touches.size > prevSize){
+      cancelSelection();
+      selectionTimer = setTimeout(startSelectionIfNeeded, 700);
+    }
   }, {passive:false});
   stage.addEventListener('touchmove', function(e){
     e.preventDefault();