I hope you've got a good optometrist, because you may need one after playing Mystery PI: The Vegas Heist, the latest hidden object puzzle game from PopCap games. MPI: Vegas is the sequel to last year's Mystery P.I.: The Lottery Ticket.

Although I don't see the point in having a plot for a puzzle game, nevertheless there is one. You're a private investigator hired by the newest Las Vegas casino, which was robbed of $4 billion one day before its grand opening. If you find the money before they open, you get a tidy fee of $50 million.

If you've ever played any of the Mystery Case Files games, you'll be very familiar with MPI: Vegas. You're given a list of about 10 or so objects to find, which are well hidden in a specific room among dozens of other random objects. You have a limited number of chances to find these items, depending on the number of rooms and items available on that level.

Rarely will the objects jump out at you, so get ready to spend a decent amount of time searching every nook and cranny of the room. To make things more challenging, the objects are represented in various forms. For example, "telephone" can mean a picture of a cell phone, an old fashioned telephone, or even the word TELEPHONE. Similarly, your list might include the phrase "long necked animal", which means you're looking for a giraffe.

If you're stuck, you can always click on the Hint button for some help. However, every time you use it, you use up one of your search chances. If you use up all your chances, clicking the Hint button again will result in points deduction. And don't get too click-happy either, because that too will cause you to lose some points.

In some of the rooms there are hidden fingerprints, keys, and poker chips. Collecting all 25 keys and poker chips unlocks Unlimited Mode, while collecting fingerprints adds point bonuses to your score. At the end of each level you encounter one of five mini-games: Word Search, Tile Rotation, Tile Swap, Jigsaw and a unique crime-solving puzzle. These mini-games offer no challenges and can be solved very quickly, but they're a nice break from staring at rooms for 5-10 minutes at a time.

Like other hidden object games, MPI: Vegas is best played in short bursts. The nature of the game can easily lead to eyestrain, especially for those with already poor vision. I can spend 6 hours playing all sorts of games, but my eyes were hurting after only spending 2 1/2 hours playing MPI: Vegas. I paced myself in subsequent bouts by playing only an hour a day in the course of a week. Still, if these kinds of games float your boat, then you'll be happy with this one.

Download a free trial of Mystery PI: The Vegas Heist, and if you like it upgrade to the full version for only $19.99.