Hello Horace!

No, the game itself doesn't need internet once you have it installed from your Steam Library.

It does need Steam running, as it launches through Steam to verify ownership. Steam's Offline Mode works fine for this, as long as you're "offline" logged into the account you purchased the game on.

Hopefully this helps!
-Nick from Journeybound Idle

Weird, when I start it with no internet, it just opens as a blank white screen, with no title bar or anything. :(

Ah, that detail actually helps quite a bit! If it was an ownership verification issue, that would actually force close the game entirely after launching it. A white screen is more likely a graphics driver or integrated GPU kicking on if you're on battery while travelling.

You can potentially try disabling the GPU in the Steam launch options. In Steam, right-click Journeybound Idle > Properties > General, and in Launch Options type --disable-gpu.

Laptops on battery often switch graphics modes to conserve power. If it works, it might lag on the Main Menu screen, but should get better once you're loaded onto your character. At least, that is the case on an older laptop I use for testing.

I'm pretty sure that should work. If not, I'm happy to try and help over Discord PMs if you want to send me the log files for the game. You can also read them to see what it says in your *\AppData\Roaming\journeybound-idle\logs folder. It might be helpful!