Run script every 30 min with systemd

I would like to execute a script every 30 min after booting into the system. I know you can use cron, but I don't plan to use this feature often therefore I'd like to try it with systemd. So far I have only found the monotonic timers which allows to execute something once (at least I think so). How would the foo.timer and foo@user.service look like in case I wanted to execute something every 30 minutes from boot/system start? **foo@user.service** [Unit] Description=run foo Wants=foo.timer [Service] User=%I Type=simple ExecStart=/bin/bash /home/user/script.sh **foo.timer** [Unit] Description=run foo [Timer] where I am stuck... ???