I don't know how to open the game. :(
*edit
Thank you for the explanation! I was able to play the game. I was quite surprised to play such a cute little game, as I was a bit scared beforehand when I saw the programming code & tools. Cute art & very simple gameplay, but it works and it was a fun little experience.
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I figured it out yesterday. Download the .P8 file, Go to https://www.pico-8-edu.com and click on play. Then drag and drop the downloaded P8 into the browser window and type in run when the cartridge is loaded. The drag and drop part was missing from the download instructions.