I stoped playing, until I need a lot of zinc and had no really upgrade for now. The splitter feels nice, I like also the idea of upgrading the fortress, maybe upgrade the fortress open also new upgrades.
Thanks a lot, this is really helpful! You're right: the tin phase has nothing to buy for too long. Next update rebuilding fortress halls will unlock new talents (your idea), mostly paid in copper, so there's always something to spend on. Glad you liked Shards and the fortress