No native multiplayer or co-op mode is listed for Big Ambitions 1.0. Steam identifies the game as single-player. [topic-1]

What to do

  • Expect one player to control the company and character in each save.
  • Treat multiplayer projects found in community channels as unofficial mods.
  • Back up a save before testing any mod that changes networking or simulation state.

Why this answer holds

The official Steam feature list includes Single-player, Steam Workshop, achievements, and cloud saves, but no multiplayer or co-op feature. [steam]

Version 1.0 check

This page covers officially supported play. It does not certify unofficial multiplayer mods or promise future support.