The kind explanation was very helpful
I liked the bxslider that I first encountered, and the technique of infinitely repeating using dot images was also good
I regret not being able to take offline classes on the Sucademy site in the past
but I would like to try to complete the course again through online classes

kunio18810012

Create a simple portfolio to introduce yourself and learn how to create a structure with HTML tags and how to style a web page with CSS properties.

sucoding

Learn HTML/CSS while creating

Thank you GunLoc for the great review. 
Many example sites use no-repeat as a must when using background images. However, it is difficult to find out when to use something other than no-repeat. If you remember that even a small 1px dot image like the video can be a great background processing technique when using repeat, it will definitely be helpful to you :)