In order for you to play Castle Crashers on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
Mac OS X 10.11 - El Capitan
Processor (CPU):
i5 2.3GHz+ or better
Memory (RAM):
8 GB RAM
Graphics Card:
512 MB video card
Hard Drive:
255 MB HD space
Sound:
Mac compatible sound card
Other Requirements:
Broadband Internet connection
Additional:
With the right drivers the game supports Microsoft® Xbox 360, Sony PS3, and Logitech controllers
Additional:
Ultra Graphics Mode requires a 64-bit OS, at least 4GB of RAM, and a 2GB VRAM.