This would have to be that laser-bluetooth type-anywhere-surface-thing keyboard. The one that comes from a light shining from a pen-shaped thing. Or it could be a large glass surface with the sort of tech that's in a Google Glass except you'd have to have touch capabilities. This could be done with resistive touch (which is less accurate which is bad for games but can deal with messes on it) or capacitive touch (which can't deal with liquids). Either way means that it's not clear...so I'm going insane trying to justify this when more of my life is spent on FS than on games.
It would only work if you could dynamically assign dead zones. If the entire screen was live, you'd be touching things with your palms and heels and errant fingers and whatnot so there'd be a lot of irrelevant input. You could create virtual buttons like on a smartphone but from my nonexistent knowledge of such technology I feel that it's a bit of a waste of technology and energy.
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But you could be right.
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But you could be right.