LAS VEGAS — Bragging rights are usually the only reward at the end of a well-played video game. But what if high scores came with cash, too? Nevada is on the cusp of what could be a casino revolution, drawing up plans for the introduction of arcade-style video games that would pay out winnings based on a gambler’s skill at, say, blasting aliens out of the sky, destroying enemy tanks or driving a virtual race car around a track.