Hi Mark, make sure to unzip the downloaded file as GB Studio won't be able to read the project file unless unzipped.
Once you have unzipped the download file and opened the project, you will be able to view lesson 3. I have made added comments that will explain all the Lesson 3 code and concepts within the project.
I recommend reading the Lesson 3 Overview Devlog as it will introduce the lesson and let you know where to find the comments:
https://gumpyfunction.itch.io/lets-build-a-platformer/devlog/813150/lbap-lesson-...