Underwater Cities

Flow: Three eras contain ten rounds, split four, three and three. Each player takes three turns per round, playing a card with an action slot. A matching card and slot can resolve in either order, but each must resolve completely before the other; do not interleave the two effects.

Actions and costs: Normally choose an unoccupied slot and perform at least part of its effect. Construction still costs the usual resources unless a card specifies a different price or says free. Resolve newly triggered rewards immediately. Draw one card at turn end and discard to three before your next turn. The colorless always-available slot can be reused but never matches a card.

Network: Tunnels must connect back to the starting city through existing tunnels, possibly across empty city sites. New cities must be adjacent to an existing city but can precede their connecting tunnels. Buildings require an existing city or a legal new-city site, and join the network only beside a connected city.

Production and feeding: Produce once at each era’s end. Connected buildings, tunnels adjacent to cities, and connected symbiotic cities produce as specified. Feed each connected city one kelp; use biomatter for any shortfall, then lose three points per remaining unfed city, never falling below zero.

Action cards: Claimed action cards normally work once per era and need a slot or effect authorizing their use. Keep at most four, including your Personal Assistant. Upgrading a structure normally costs one science, and an upgraded structure cannot be upgraded again.

Special cards: Taking one into your hand does not require paying its printed credit cost; pay when playing it with a matching slot. Discarded one- or two-credit Special cards return to their deck’s bottom. Keep paid instant Special cards under your board so they cannot circulate again. Only six three-credit cards are initially offered, without replacement.

Final scoring: After the third Production and feeding, score metropolises and end-scoring cards. A connected city with zero, one, two or three building types scores two, three, four or six points. Sell biomatter for two credits each, then convert each combined four credits, kelp, science or steelplast into one point. Most points wins; ties use the order determined after the final round.

Solo: Use an advanced player board and the two-player main board. Three non-player action tiles move clockwise each round; failing to advance on the Federation track adds a randomly blocked slot next round. After ten rounds, win with at least seven connected cities and at least 100 points. Do not use government contracts.