My Take
My students love it. I love it. I recommend to anyone teaching coding to high school students.
It was so successful that I had several of my advanced students teach themselves JavaScript and Python.
I would place this on the Modification level of SAMR because of the significant functional change to the task of writing a we page in coding when compared to Notepad or Notepad-plus-plus.
How I Use It
I used this site with my web page publishing students to learn HTML & CSS. The live preview of the website as the code is entered is highly dynamic and allows students to see effects of coding in real time to add meaning to the sometimes nonsensical symbolism.
I worked through the curriculum at the pace do the slower learners as a group using my projector and the more advanced students could work at their own pace with many different options for those who complete early.
There Is a points reward system that students can get points during the lessons and the mini games. The mini games are content rich and engaging.
There is a certificate available at the end of the unit. There is a note pad where students can store notes and access throughout the courses. There are links to relevant sources through the course.
There is even a theme song about coding my students memorized and would sing down the halls at school.