In order for you to play Penumbra Overture on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
OS X 10.7.5 - 10.15.0 This product is not compatiable with macOS 10.15 Catalina or later.
Processor (CPU):
2.0Ghz
Memory (RAM):
1024MB
Graphics Card:
Radeon 9600/GeForce 4 (GeForce4MX not supported, Integrated graphics might not work.)
Hard Drive:
2.0GB