Oh, I make a lot of mistakes 
but opamps seem to be my true nemesis.
Let’s see, same signal to both inputs, misconfigured feedback loop (salvagable), swapped power lines (salvagable!), and now this.
(All these mistakes were made in EasyEDA and when using stock components, so have switched to my own footprints 
. I also wonder if the extreme ease of use of a browser-based EDA hasn’t been a factor here – at least a couple of these were drafted on some random laptop that I couldn’t have run Eagle/KiCad on, and only turned into a PCB later, in the “do I have something else that could go in this PCB order” phase…)