My mom's experience with videogames largely consists of watching me play Final Fantasy IX and X and offering such helpful advice as, "Why don't you just cut his head off with that big sword?" and, "Don't you have a gun? You could just shoot him and be done with it." Her own gaming career came to an abrupt halt several years earlier when she learned that jerking the controller left, right, up, and down doesn't actually make Sonic move. There's a level of abstraction necessary to make the correlation between a button-press and on-screen action, a bridge we were never able to cross together.

The impulse to cross that bridge is currently driving the home console market and has been doing the same in the mobile gaming space for years. In a blissful marriage of concept and execution, it's an impulse that Esquilax Games have nailed with Climber Brothers [$0.99/Lite], a delightful little puzzle-platformer in which players are tasked with guiding the titular brother-climbers to safety through a set of increasingly difficult physics- and momentum-driven levels.

Esquilax wisely pared Climber Brothers down to one mechanic: when your right and left thumbs are touching the screen, Greg and Jeff (respectively) jam their picks into the rock face. When you let go, they let go.

It's not just that the controls are responsive and precise or that the physics in Climber Brothers feel spot-on, it's that the catch-and-release mechanic takes full advantage of the iPad's tactile interface to match an extremely basic input (thumb touching the screen) with a physically analogous output (climber touching the rock). The result: one brother serves as a fulcrum as the other swings around, carried by his momentum, to his next anchor point; from there, repeat ad infinitum, or until you've reached the safe zone.

I'm tempted to situate Climber Brothers somewhere between the ice climbing section of Modern Warfare 2 and full-blown Kinect gameplay. In the Call of Duty level, the right and left triggers replace your thumbs as input devices, but the emotions are the same � the tension in your hands, the mounting desperation coupled with the tactile joy of progress: right, left, right, left. What makes the physics-based Climber Brothers more interesting, though, is heat death � when you run out of potential and kinetic energy with which to create momentum, no matter how desperately the Brothers cling, the game stops: players have no choice but to let go.

"[H]e reflected that when one gets properly wearied, drowning must really be a comfortable arrangement, a cessation of hostilities accompanied by a large degree of relief, and he was glad of it, for the main thing in his mind for some months had been horror of the temporary agony. He did not wish to be hurt."

That passage, from the end of Stephen Crane's "The Open Boat," is about drowning, but it could just as easily be about climbing. Back in Climber Brothers: your thumbs begin to cramp and your mind races, searching for some way to violate the laws of conservation of momentum, but you realize that Jeff and Greg are truly lost. After that split second of fatalistic anguish, letting them drop comes as a relief and the Brothers carry a morbid grin as they plummet.

At least Esquilax Games has a sense of humor.

And so there's a certain pathos to maneuvering the Brothers around, plotting your course, solving puzzles. You realize acutely that you hold the Brothers' lives in your hands more directly than usual, thanks to that tiny, incremental step in physicality.

But there's a secondary pleasure, borne out of Climber Brothers' finely-tuned physics engine: flight. Climber Brothers has a fantastic learning curve that introduces its physics organically and unobtrusively. Esquilax doesn't teach you how to slingshot your beleiderhosened avatar around so much as its level design ingratiates the concept into your subconscious. I don't remember when I�learned how to do it, but I know now and I didn't earlier.

And once the baseline mechanics have been laid out, Esquilax iterates in several different ways � some levels require the Brothers to use their momentum to hook around sharp angles and ledges; others are about maximizing speed without sacrificing height; others still are about freefalling through gaps just so.�Don't get me wrong � there's something empowering about solving puzzles, but the avian joy of through the air � like a duo of portly, vaguely Teutonic Spider-Mans � particularly underscores the simple grace of Climber Brothers.

There are certainly some issues: the music loop is short and taken from a collection of stock tunes (our forums point out that the same music is used in Storm in a Teacup [$2.99]), and some elements of the map have special properties (can be landed on, can't be grappled, will kill you,�etc.) that aren't always clear. But Climber Brothers is remarkable in its ability to match its core conceit to both its mechanics and interface, and then to mix, match, recontextualize, and refine as needed. It's finely crafted, well presented, and precisely executed.

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