I was doing other tutorials with the only problem of not being able to access the libraries without copying the files to the project directory. That was solved by copying and I was able to move forward with several of the tutorials.
Now I think I have a problem related to that but that I am not able to solve:
There are no methods that should be included in the Button and Slider classes.
See the image, does anyone have any ideas?
PD: It is rare that error is marked in lines where it does not correspond.