The Dink Network

Yes, it's too bad there aren't sine/cosine functions in Dink, and you'll need floats too. But I guess you could do something sp_mx() and sp_my(). I don't know exactly what they do, but I think it sets the x/y component of the speed of the sprite.

I didn't check redink.exe, but if it has sine/cosine and floats you can make circular movements, setting the sp_x and the sp_y. You'll have to change the sp_dir manually, though.