Mystery P.I. Portrait of a Thief is a "seek and solve" game (a very popular genre of games for both kids and adults – it was actually the most played genre of games online in 2008) for the Nintendo DS that tasks players with finding a variety of smaller images hidden within one larger picture.
In the main game, you play as a famous private investigator on the hunt for an art thief, and you must play through 20 chapters that take you through a variety of distinct settings. Each chapter contains a handful of environments filled with hard-to-spot smaller images, such as birds, phones, food, and other common items. Because the overall image is much larger than can be clearly seen on the Nintendo DS screen, you'll see a zoomed-in portion of the scene on the touch screen that can be moved around by dragging the image with your stylus. When you spot one of the items you're supposed to locate (listed on the top screen at all times), simply click it to remove it from the screen and cross it off your list. A hint system lets you occasionally click a button to highlight an area where one of the remaining items is located, though you'll take a score deduction in the process.
When you find the required amount of clues in a chapter, you'll complete it by playing one of five distinct mini-games, including Memory Match (where you match like images on the touch screen), Jigsaw Puzzle (arrange the pieces to create the image), Tile Rotate (shift the tiles to display the proper scene), Word Puzzle (find hidden words in a jumble of letters), and Mah-jongg Match (clear the screen by matching like tiles). These mini-games can also be unlocked for free play by finding hidden keys in the primary game settings.
Mystery P.I. Portrait of a Thief is rated "Everyone" by the ESRB with no content descriptors.