If you want to run on a different host then localhost, you'll need to set the following environment variables:
storeys_gui = http://<EXTERNAL-IP>:7070/index.html
Also https://www.learn.study/ops.html (pending #276).
A Series N1: f1-micro (1 vCPU, 614 MB memory) is too small and crash loops; but a Series N1: g1-small (1 vCPU, 1.7 GB memory) seems to suffice for 1 or 2 player; otherwise a N1 standard or a e2-medium (2 vCPU, 4 GB memory) or more is recommended.
Remember to set the environment variables as above, add a persistent /data volume, and create an appropriate firewall rule.
TODO Cost: $x VM + $y PD + $7 (?) static IP + $z Ingress+Egress = $TBD.