Summertime.7z -

A free tool for macOS users to handle these files. Steps to Extract: How to Use 7-Zip to Compress Files and Extract Files

The native tool for this format. You can download it for free at 7-zip.org . summertime.7z

To access the game, you must extract the contents of the archive using a file archiver: A free tool for macOS users to handle these files