unicode animation in bourn shell

#!/bin/sh

a1="◐"
a2="◒"
a3="◑"
a4="◓"

i=1
while true
do
	eval char=\$a$i 
	printf "%s\r" $char 
	i=$((i+1))
	if test $i -gt 4; then i=1; fi
	sleep 1s
done