okie, i have never used a Mac b4. so i jus have this simple question: can a Mac-based game use directinput8 api? or how simply, does Macs allow the installation and usage of directx8?

No, you cannot use DirectX in anything except x86 Windows environments. Take a look at SDL (libsdl.org), it''s portable to MacOS (as well as Windows, Linux, FreeBSD, BeOS, and so on). Remember that PPC processors are big endian, while IA-32 CPU''s are little endian, you have to be careful of that when loading and saving files.