Vim: set "cursor keys" hjkl to wasd

I wish to overwrite/remap the basic vi/vim (and gvim) "cursor keys" **hjkl** to the ordinary "gamer layout" **wasd** (w-up, a-left, s-down, d-right). Moreover: I know that "w", "a", "s" and "d" are important keys in vim so I came up with the idea to remap **hjkl** to **ALT + wasd**.