A node cloned into the page for an animation is still matched by the selector that produced it

Fact

The usual way to fly an element somewhere — clone it, position the clone absolutely, animate the clone, drop it — leaves a node in the document carrying every class the original had. The next run of the same effect selects the originals and the clones still in flight, and clones those too. Each run multiplies, so a surface that animates once per user action ends up with hundreds of invisible nodes in <body>.

Why it matters

The clones finish transparent, so nothing looks wrong. What shows up first is a slow leak — memory, layout cost, and every later querySelectorAll on that class returning more rows than there are real elements, which quietly breaks logic that counts or iterates them.

How to apply

Select from the container the real elements live in, and exclude the flight class explicitly:
```
document.querySelectorAll('.seat .chip-stack:not(.flying)')
```
Sweep leftovers at the start of each run; an animation whose promise never settles otherwise leaks forever.
Strip id attributes from a clone. cloneNode(true) copies them, and a duplicate id makes getElementById resolve to whichever came first.