Today I lost 600+ gems because I just did tap-tap. At the first tap it displayed the number of gems it will cost me because all builders were busy, at the second tap I've spent all of them to pick up a log… Only then I realised what I've done. Too late, 600+ gems unnecessarily spent. Stupid mistake on my part, I know. But maybe you could add some short-term Undo option for such situations? Let's say, undo within 10-30 seconds?
