In order to play Alex Kidd in the Enchanted Castle on Linux with maximum graphics settings, you need a computer with a configuration no worse than the following
OS: Ubuntu 16.10 or higher
Processor: Intel i3-2100 or AMD Phenom II X4 940 or equivalent dual core CPU
Graphics: NVidia GeForce GTX 280 or ATI Radeon HD 6630 or equivalent DirectX® 9c or higher 1GB VRam