Hi Rui and Sarah. I am really enjoying your new graphical display book. I seem to be having a problem controlling the green LED on the ESP CYD board. I was modifying the basic button sketch to include a toggle switch to turn the green LED on and off. When the toggle was pressed the sketch output the relevant log info ie
toggle_switch_event_handler: State: On CYD_Button_Two_States_and_switch.ino:100
  However it would not turn on. I tried changing the pio pin number  from 16 to 4 ie green to red and the red LED worked perfectly with the same sketch. I then tried a simple sketch to directly set up pin 16 to be an output and then using digitalWrite and a delay turned the LED on and off. This worked fine and the Green LED duly flashed a expected. Is pin 16 being used by something else when controlling the display?