Making progress on the “green bubble problem” - level bubbles no longer turn green without code changes

In the past, we have gotten many reports of students in CS Discoveries and CS Principles advancing quickly through levels without changing any code and still having their levels marked as “completed” (solid green level bubble). This caused confusion and frustration for teachers because levels that had no work done on them looked the same as levels that students have completed correctly. Hence, the “green bubble problem.”

On most App Lab, Game Lab, and Web Lab levels in the 2020-21 versions of CS Discoveries and CS Principles, we now require students to change code before their level bubble turns green. If the student does not change code but tries to advance anyway using the ‘continue’ button, they will be warned to keep working. If they choose to proceed to the next level, the level will be marked “in progress” (white bubble with a green outline) instead of “completed” (solid green bubble).

While these levels are still not fully validated (see why we don’t fully validate all levels), we hope this will provide a small ‘speed bump’ for students who are racing ahead and make teachers’ lives easier!

We’d love to hear how this is working for you in your classroom - reply to this forum post to let us know, or feel free to reach out to

What is considered a “code change”?

Any change to the text in a level’s code editor is considered a code change. Adding or removing whitespace (spaces, tabs, newlines, etc) is not considered a code change, but adding or removing a comment is. Changes to images, assets, or design mode elements in App Lab are also not considered code changes. Levels where no code is expected to change have had this functionality disabled.


WOW! CODE.ORG DOES IT AGAIN! Unfortunately, I’m teaching Google applications instead of Code this semester due to school needs. I can’t wait to get back to teaching code!

Jenny Brandon

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