On Mars
Can I build or upgrade on a hex with a Crystal?
The designer answered this directly in 2020.
- newrev · Designer · 2020-01-03
- MattDavisFLA · Community · 2020-02-06
- Geroid · Community · 2020-02-06
- joetweber · Community · 2021-03-08
You can construct a building on a hex with a Crystal, which returns it to the supply, but you cannot upgrade there. Crystals only sit on empty hexes, so an existing building never has one; the page 13 wording that seems to say otherwise is a typo.