Portal needs no introduction. It's a short, but dense game. A fantastic melding of puzzle and first-person shooter, that had me scratching my head as a kid. Some wonderful environmental storytelling, active cutscenes keep the pace steady, and a unique and substantial amount of mechanics that continuously get added, level after level. A satisfying finale that brings together all that you've learned. Visually, it is no longer cutting edge, but still looks fantastic for the time. Portal 2 improves upon it in so many ways, but it is still worth visiting this gem, to see where it all began.