Select an object for a time to start a command. Light
If the segments f or g are selected for few seconds, then f will be deleted and g will become red.
A text, written with the red color, tell you when these objects are selected.
If you stop the selecting before the duration needed, then f and g are not changing.
For "wait=1" the duration is around 5-6 sec, if you want more, incress "wait"