#imgTumbling1 {
  margin-right: .5em;
  border: 2px solid black;
}
#imgTumbling2 {
  margin-right: .5em;
  border: 2px solid black;
}
#imgTumbling3 {
  border: 2px solid black;
}
#imgTumbling4 {
  margin-right: .5em;
  border: 2px solid black;
}