If you don't see the little dot at the bottom moving then click the green flag again. This is an internet speed test. To give you perspective, if you got 15 it is at about a 62.3 Mbps download, your Internet connection should be able to handle multiple devices streaming HD videos, video conferencing, and gaming at the same time. Nov-9-2020- I made it so it works on safari. Nov-11-2020- I added something to let you know when it is testing if you are connected to the internet.
Thanks to @Chiroyce for inspiration! Check out his internet speed test here- https://scratch.mit.edu/projects/424893697/