The Create a Custom Front Page With a WordPress Theme Template could be better.
First the coding environment should be very basic and simple. That development file structure should not be in a tutorial. The tutorial author should have created a new installation of Wordpress and started fresh with just the 3 default themes from a brand new install.
A correct setup for the viewer is important to replicate what they may be seeing when they install and start creating a child theme.
Second, take the time to use current code standards with includes enqueuing the stylesheet. The functions file is being used anyway in the widgets tutorial. Wordpress states "using @import: this is no longer best practice, as it increases the amount of time it takes style sheets to load. The correct method of enqueuing the parent theme stylesheet is to add a wp_enqueue_scripts action and use wp_enqueue_style() in your child theme's functions.php."
Third, cowboy coding and hand typing out the code with long silence, is awkward. Write the code ahead of time copy and paste the correct code line by line and explain each one. The time it took to write out the code, another section explaining enqueuing the stylesheet correctly could have been made. The complexity of the widget code far exceeds that of the enqueuing code in the functions.php.