Yuji Naka's company Prope, developer of Ivy the Kiwi? and Let's Tap, has been quietly populating the iOS App Store with Let's Tap minigames and other assorted bite-sized apps, but its latest release is something of a surprise.

PD - prope discoverer is an Unreal Engine-based game for iPhone and iPad that has players exploring a 3D castle environment to find three hidden cards in each area to unlock doors. It's sort of a hidden-object game, but with first-person movement and a fully rendered 3D world.

Prope Discoverer is definitely a mellower experience than Infinity Blade, but it's interesting to see a small Japanese company developing a first-person Unreal-based experience on iPhone. If you want to walk around the "idyllic sunlit gardens" and "eerie and bewildering castle cellars," you can download it for $3. Wander past the break for a trailer.

This article was originally published on Joystiq.

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