html, body {
  margin: 0;
  padding: 0;
  height: auto;         /* let content define height */
  min-height: 0;
  overflow-y: auto;     /* scroll only when content is taller */
  overflow-x: hidden;   /* no horizontal scroll */
  overscroll-behavior: contain; /* stop scroll chaining/bounce */
}
#app { min-height: 0; }