How do you build a smelter?

Question

My smelter "button" currently reads:

Smelter (0|0)

They appear to cost 200 minerals. The +/- buttons enable themselves when I have >200 minerals. When I hover over the "+" button, a "+all" appears below it. If I click the "+" button, nothing happens, as far as I can tell. (It continues to read "Smelter (0|0)".) The "+all" looked like maybe it needed a kitten, so I free'd up a kitten, but to no avail.

I don't know how to produce iron, and I don't think I've successfully produced iron ever. (This is holding me back from some of the workshop upgrades, such as iron hoes & iron axes.)

I've researched up to Philosophy, Machinery and Steel. (i.e., those techs are not yet researched, but everything before them is.)

How do you build a smelter?

Answer 1

You have to click on the button part with the text, just like with any other building (most don't have + button, so it may seem confusing at first). The + button is for increasing the active levels after you have it bought.

Since it uses up resources when active, it has +/- buttons to increase and decrease the active levels of smelter, in case you want to free up the resources that are being used by it.