Hi! Thanks for checking our game out! :)
The control scheme is admittedly a little complicated but it's the only way we could make it work reliably. To make a campfire, you first make a firepit by putting a stone on the ground by selecting the stone card and right-clicking on the ground near the player. Then you select another stone card and left-click the stone you placed on the ground (or you can just use a stone that's already on the ground). Same then with using logs in the firepit using left-click etc :)
It's always left-click to pick up and combine, right-click to drop some items on the ground.
Hope this helps!