Hello! What version is your macOS? Also, did you download the game using the itch.io app? That tends to solve the majority of issues with this version. The next version is coming soon, so mac users can play the Arena Royale mode, but due to a bug I found while making the shrinking circle, it will take awhile to get the next update out. In the meantime, I am working on a multiplayer game which will have an online multiplayer update soon.
Thanks!
ProjectTetraDev