> On the other hand, I think the user would rather expect "Space" for confirmation of highlighted items. I think we should try out both (just assign the key twice for testing) and see which one feels better. Maybe even leave them assigned twice in the end if there are no collisions.

There may also be a simple switch integrated into the games settings to choose the prefered method.

> Concerning the ALT key: I would use CTRL instead. Iirc, there was some trouble on either Linux or Mac with ALT combinations being reserved for some system stuff. I would rather avoid the ALT key.

I can tell at least for OS X that "Ctrl + Left Mouseclick" is a bad choice because that is the systems shortcut for a right click. From personal experience with developing cross plattform webapps I can tell that the ALT is the one that this (at least in browsers) works best across operating systems.

> Using 1-5 to put stuff directly into the numbered inventory slots: This means we cannot use the number keys to directly select Tabs in the menu. I'm not sure which feature is more important. I would like to have a key to go directly to a tab rather than having to cycle through them.

Good point. I added the suggestion that this behaviour can be preserved with the combination of "ALT + <Number of the Container>".

> Also, you didn't mention it but I guess W and S should be used to go up and down through different interactions? (e.g. go from inventory to production in producers and select through stuff like the various pump interactions)

Thanks. I updated the concept with a matching sentence to include this.