"Mark of the Ninja" review: Best stealth game on Xbox Live? Klei Entertainment -- the studio behind such popular downloadable video games like "Eets," "N+," and "Shank" -- tries its hand at the stealth genre with "Mark of the Ninja." It tells a simple story that's interesting enough to keep you from skipping cut scenes, all the while, dripping with a slick shadowy atmosphere, but the real draw is the clever and fluid side-scrolling gameplay. Being a ninja, you'll spend a lot of time sticking to the shadows and using your senses and upgradable gadgets and abilities to get the best of your enemies. The environment is your friend, but you'll have to master it first. Slipping through, over or under your surroundings is made all the more interesting by a clever use of a sort of "fog of war." You can only see on screen what falls in your character's line of sight and footsteps are visually represented on screen when enemies are nearby, but out of view. Stages are tough and riddled with obstacles, traps and hidden challenges. You'll want to create a few shadows of your own to get the drop on your enemies. Extra points can be earned for stealth kills, remaining undetected, making successful use of traps and distractions and hiding bodies (or cleverly displaying them). Completing the game presents players New Game Plus, which offers a higher level of difficulty and turns off all of the game's help effects but still allows all of the gadgets and abilities you've upgraded so far. This and an unnerving drive to perfectly and silently complete every level gives "Mark of the Ninja" a healthy dose of replay value. Mark of the Ninja is rated M for Mature by the ESRB. It is available now on Xbox Live Arcade and PC.