/* ===== Bootstrap custom CSS – HW2 ===== */

html, body {
  margin: 0;
  padding: 0;
}

/* Every visible block */
.box {
  border: 1px solid red;
  box-sizing: border-box;
  min-height: 100px;
}

/* Heights to mimic original layout */
.h20 {
  min-height: 140px;
}

.h40 {
  min-height: 280px;
}

/* Mobile behavior */
@media (max-width: 750px) {
  .h20,
  .h40 {
    min-height: 120px;
  }
}