The Deadseat

The Deadseat nests one game inside another, you're playing a handheld game in the back seat of a car, and what you find in that inner game somehow crosses over into the real back seat, which turns ordinary handheld progress into your only actual defense.

Because items only matter once they've crossed from the handheld screen into reality, treating the inner game seriously rather than as flavor text tends to matter more than it first appears, an item ignored inside the small screen simply isn't there to use against the creature outside it. The short length is deliberate, built for one focused sitting rather than a long session, which keeps its central twist from wearing thin. The Baby in Yellow offers a similarly short, creatively unsettling horror experience in a very different setting.