Challenge 1: Add Escape-to-Close to the Modal — Possible Solution
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function openModal(modal, triggerButton) {
  const previouslyFocused = triggerButton; // Ch.4 Step 3 — remember who to restore focus to

  const focusables = modal.querySelectorAll("button, a, input, [tabindex]");
  focusables[0].focus(); // Ch.4 Step 1 — move focus in

  function closeModal() {
    modal.setAttribute("hidden", "true");
    modal.removeEventListener("keydown", handleKeydown);
    previouslyFocused.focus(); // Ch.4 Step 3 — restore focus
  }

  function handleKeydown(e) {
    if (e.key === "Escape") {
      closeModal();
      return;
    }

    // ...existing Chapter 4 Tab-trapping logic goes here too...
  }

  modal.addEventListener("keydown", handleKeydown);
}

WHY THIS WORKS
--------------
- previouslyFocused captures a reference to triggerButton — the
  element that had focus immediately before the modal opened — at the
  very START of openModal(), before focus moves anywhere else. This is
  the specific detail Chapter 4's own Challenge 3 identified as
  missing when a modal fails to restore focus correctly: capturing the
  trigger reference has to happen before Step 1 moves focus away from
  it.
- handleKeydown checks specifically for e.key === "Escape" FIRST,
  before any Tab-trapping logic — if Escape is pressed, closeModal()
  runs immediately and the function returns, without falling through
  to whatever Tab/Shift+Tab cycling logic exists elsewhere in the same
  handler.
- closeModal() does three things in order: hides the modal, removes
  the keydown listener (so it doesn't keep intercepting keys on a
  now-hidden element), and calls previouslyFocused.focus() — this last
  call is Chapter 4's Step 3 in action, returning the user's focus to
  exactly the button that opened the modal, rather than leaving focus
  "lost" the way Chapter 4's own Challenge 3 scenario described.
- Removing the keydown listener inside closeModal() is a necessary
  cleanup step often missed — without it, a stale listener could keep
  firing (or accumulate duplicate listeners) if the same modal element
  is reused and reopened multiple times across a session.