I can't play :(
Hello! Try these steps and let me know if it works for you.
1. Move the application to your Applications folder.
2. Open Terminal.
3. Paste
sudo chmod +x /Applications/RadiantsDemov2.1_Mac.app/Contents/MacOS/The\ Radiants\ Alpha\ Build
then press Return/Enter.
4. Enter your password when prompted and press Return again.
5. Open the Radiants application.