Summary:
Co-op no longer routes gameplay through the hosted server. Players connect directly: same-WiFi is instant over the local network, and players across the internet go peer-to-peer with the server only handling lobby matchmaking. Loading a co-op save now takes the host to the lobby first with each player's slot reserved, Start locked until everyone is back, and the saved world restores structures and placement correctly. A handful of performance and polish fixes round it out: large-base production is faster, lobby visuals are smoother, the pause tag no longer flickers on remote players, and the window reliably reopens on its last monitor.

Changes:

1. Direct connection between players — server now only handles the lobby and matchmaking; all gameplay runs peer-to-peer with no server in the middle.
2. Same-WiFi players connect instantly over the local network, no internet needed.
3. Loading a co-op save now goes to the lobby first — each player's slot is reserved, and Start waits until everyone has rejoined.
4. Co-op structures, consume, and placement sync correctly.
5. Large-base performance improved — production lookups optimized for bases with many structures.
6. Fullscreen and lobby visuals smoother — reduced metaball and fullscreen render overhead.
7. Pause tag no longer flickers on other players' nameplates.
8. Window position and monitor remembered — borderless/fullscreen restores to the correct monitor, windowed mode stays centered on its last screen.