Linux support?
What about other OS'es?
You are using DirectX 9 for 3D and heavy use of Win API and DirectX for sound and input as well.
I ask you to at least consider a Linux port. SDL and OpenGL can do nearly everything DirectX can. Also this leaves the door open to MAC ports as well.
If not then some compatiblity testing with WINE would be appreciated, as it is always getting better at running Windows software. A few tweaks which would be invisible to a windows user may make or break a WINE app.
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Thanks for reading!