Flesh player

Flash Player is a language runtime, similar to Java.  Game developers write an application, compile it to bytecode, and pass it to Flash Player.  We handle all of the low-level stuff like rendering pixels, allocating and deallocating memory, etc.  

It's totally possible to write a game that uses resources efficiently, but that doesn't always happen.  There's not much you can do about it, or that we can do about it at a generic language, compiler and virtual machine level. 

The right answer here is to talk to the game developer; however, since Flash Player reaches it's End Of Life on December 31, there's probably not a compelling reason for the game developer to make additional investments. 

Short of fixing the game, you can try closing everything else on the machine but the one tab with the game, to minimize resource contention, or find a faster machine.  Those options aren't great.  The easier answer is probably to just find a different game to play that's built with either web-native technologies or runs as a native desktop application.

Also, for convenience, here are links to the Flash Player uninstallers.  We're encouraging people to uninstall Flash at this point, since we're no longer releasing updates (including security updates) for it.

Uninstall Flash Player - Windows:
https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

Uninstall Flash Player - Mac:
https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html