Actually, scratch that. Thumbs are particularly bad at following that rule, especially when they're the haplessly opposed pair of Ilo and Milo.
ilomilo asks you to reunite the waddling pair of stout, endearing and ever-forgetful thumbs in a whimsical maze of cubes. Their topsy-turvy neighborhood puts them at a distinct disadvantage when it comes to navigation, with different orientations, levels and walking angles delaying Ilo (the red one) and Milo (the blue one) from their elate greeting. It's an elegant, often devilish puzzle game wrapped in presentation that's just too vibrant and earnest to resist.
If you're playing alone, you'll switch between Ilo and Milo frequently as you pull them toward each other, as if you're an invisible, shrinking rope that connects them across the uneven landscape. They can each carry and lay down one of several different animal blocks (that become cute little backpacks during transportation), with the simplest one closing a gap in a path. Some have more complex effects, like dropping a character through a trap door to the opposite side of a cube, and one even rolls around the level once you set it free. Transferring items between the travelers, when proximity allows, is essential and will remind you that making sense of the skew scenery is only half the challenge when you're keeping track of two moving points.
The more difficult levels require patience, observation and quite a bit of experimentation when you've lost track of which side is up, yet Ilomilo never frustrates. Solutions always conform to a limited number of rules, and each new puzzle block is introduced within the barely visible confines of a small tutorial. The game's rigid construction also prevents you from getting too lost, as your travel options will always be limited to a path of connected cubes. Best of all, you can press B to gauge your progress -- and make Ilo and Milo wave at each other. Hi!
ilomilo always remains appreciative of your double-traversal, littering its paths with collectible bits and bobs that can unlock bonus levels (featuring some indie game cameos), concept art, a retro-themed minigame and quaint letters between friends. Those are the obvious in-game rewards, granted alongside less explicit ones, like just making out the oversized, out-of-focus props that float in the background of each chapter, or hearing another one of Daniel Olsén's playground tunes. I'm convinced he captured most of the soundtrack by driving a 20-year-old ice-cream truck over a pile of abandoned xylophones.
My apprehension toward abandonment is exactly what kept me coming back to ilomilo, because I couldn't bear to leave those errant thumbs unsupervised (in the game, I mean). Seeing them reunited every time was a much better reward than an obvious proclamation of "PUZZLE SOLVED" -- so much so that I would always make Milo look away, knowing that he'd soon spin around in surprise and be happy that his friend had finally found him.
This review is based on a copy of the game purchased and downloaded from Xbox Live Arcade. ilomilo is now available (to everyone) for 800 Microsoft Points.