Two of Valve's undisputed classics are making their Android debut today, courtesy of Nvidia's Shield console: Portal and Half-Life 2. Costing $10 each, the two games were ported by Nvidia, which explains why they're only playable on the Shield. Still, the job has been done with Valve's unreserved blessing and a promise by Doug Lombardi that you "can expect the same gameplay" as on the original PC versions. Even if the recreations aren't perfect, having two of the PC's greatest titles available on the Shield brings it a lot closer to its promise of being a true mobile console. With a price cut to $199 and a growing library of games and features, Nvidia's efforts at recreating PC-class gaming on an Android portable are looking increasingly compelling.