sturdy obsidian
You know sometimes when you're trying to craft something and you accidentally click the craft right next to it? Particularly if you're limited on time or resources, and then you're forced to either wait for the wood to replenish, or you've used up a precious resource like golden artifacts on a piece of gear you've already filled out in your collection book? Perhaps there's a time when you've clicked too fast and you accidentally sold a piece of gear that wasn't even supposed to be on your shelves because it was a legendary piece of gear meant for your heroes?
Yeah... wouldn't it be nice if there was a handy undo button? I'm not saying it should be able to undo ANYTHING, but maybe up to the last three sales or crafts? Hypothetically speaking if you exit the shop titans client fast enough you can sometimes have a sale or some such not have registered, but it would be nice to have an official capacity to do so.
woven solar