You can also just use a \r directly without a \n. For example:

    spin='/-\|'
    while true; do 
      i=$(( (i+1) % 4 ))
      printf "\r${spin:$i:1} Working..."
      sleep 0.1
    done

By the way yes, that is a subtle reference to the TOS computer, so it's best read in that voice :-)