Throughout December, Gamasutra will be presenting a year-end retrospective, discussing notable games, events, developers, and industry figures of 2008, from the perspective of our position covering the art, science, and business of games. Previously, we tallied up 2008's top disappointments, downloadable titles, and overlooked games. Next, we'll cover this year's top five gameplay mechanics (with ten other honorable mentions), calling attention to a number of innovative, novel, or particularly well-executed individual elements of game design from throughout the year. The games picked are the editor's choice, and are chosen from the titles released in North America during 2008's calendar year to date, with eligible titles spanning home consoles, handhelds, and PC. For these broad purposes, "gameplay mechanic" can refer to an input method, a character action, rules affecting the game world, and so on. Generally, features were considered only if they were meaningfully implemented in their franchise for the first time, which in most (but not all) cases excluded sequels. They did not need to represent the first time any such feature has been implemented in a game, if they demonstrated particular excellence or importance. Games are listed alphabetically; no order of preference is implied. Top 5 Gameplay Mechanics of 2008 Braid (Jonathan Blow/Number None; Xbox 360) Mechanic: time manipulation Braid is not the first game to incorporate a time manipulation mechanic, but it is surely the first game to integrate one so crucially, permeating every moment and puzzle to a degree usually reserved for basic actions like running and jumping. And each world was treated as a gameplay variation on the theme of time, taking that central mechanic and expanding it in elegant ways. The pervasiveness of that mechanical theme even extended to the game's narrative and protagonist, putting a gameplay property front and center in the kind of thorough way that remains surprisingly infrequent in game design, which makes it all the more impressive on the part of designer Jon Blow that the mechanic itself is so unusual. Left 4 Dead (Valve/Valve South; PC, Xbox 360) Mechanic: cooperative player assistance, AI director Cooperative play has been undergoing a welcome renaissance lately, and Valve's recent zombie-themed shooter has reached a new high in the balance between genuinely necessary cooperation and individual agency. Some games simply drop multiple players into an otherwise single-player campaign, and some become cumbersome in their devotion to constant cooperative acts, but Left 4 Dead's simple player-to-player assistance interactions -- not to mention the inherent benefit of cooperation engendered by the setting -- make group coherence eminently rewarding and manageable, even with random online players. To cheat another mechanic into this entry, the game's AI director -- which oversees item and enemy spawning based in part on player behavior -- is a brilliantly seamless method by which to not only promote replayability, but to feed into the intrinsically frantic nature of a four-player close-quarters FPS. And after all, if you start to suspect the game is out to get you, the urge and ability to fight back is all the more intensified by having three comrades-in-arms on the other end of a headset. LittleBigPlanet (Media Molecule; PS3) Mechanic: real-time level editing LittleBigPlanet is as much about enabling gamers to participate in level design as anything else, which means its user design experience needed to at least approach the level of accessibility seen in more traditional gameplay. Certainly, creating a LittleBigPlanet level requires more investment of time and creativity than playing a LittleBigPlanet level, but it is telling that the lines between the two can be somewhat blurred. It is perhaps even more telling that, thanks to the game's intuitive, real-time nature of level editing, Media Molecule has shipped a creation mechanic that has proved enormously usable for end users while remaining standard issue for the studio's professional designers. Mirror's Edge (Digital Illusions CE; Xbox 360, PS3) Mechanic: first-person parkour The demo for Mirror's Edge generated considerable gamer hype based on the surprising fluidity and elegance of its central hook, first-person freerunning amidst a cleanly-defined urban setting. Despite taking criticism upon full release for inconsistency and certain presentational elements, developer DICE nonetheless achieved an impressive feat with the implementation of the game's character control. Combining a simple control setup with the immediacy of the first-person perspective, DICE translated a gameplay idea that had previously been well-explored in other formats into something extremely fresh. Spore (Maxis; PC) Mechanic: procedural character creation Arguably the most significant gameplay feature of Will Wright's latest offering isn't even a direct part of what gamers would traditionally call its core gameplay, but Spore's procedural character creation mechanic can become an entire game unto itself. Incorporating dynamic skeletal systems, animation, texturing, and more, Maxis achieved astonishingly robust results in an area of game design that in practice often ends up stilted and too-obviously artificial. The tens of millions of diverse creatures and structures that have been generated demonstrate the diversity of Spore in particular, but the successful implementation of the technology should be encouraging to the development community at large. Top Gameplay Mechanic Honorable Mentions Audiosurf (Dylan Fitterer; PC): dynamic music-based level creation Bangai-O Spirits (Treasure; Nintendo DS): auditory level sharing Dead Space (EA Redwood Shores; PC, Xbox 360, PS3): enemy limb dismemberment echochrome (SCE Japan Studio; PS3): Escher-esque perspective manifestation Fallout 3 (Bethesda Game Studios; PC, Xbox 360, PS3): VATS combat Far Cry 2 (Ubisoft Montreal; PC, Xbox 360, PS3): day/night and weather cycle NHL 09 (EA Canada; PC, Xbox 360, PS3): fully human-controlled teams PixelJunk Eden (Q-Games; PS3): swing-based movement Tom Clancy's EndWar (Ubisoft Shanghai; Xbox 360, PS3): unit voice control World of Goo (2D Boy; PC, Wii): physics-based lattice building Amusing Gameplay Mechanic Special Mentions Army of Two (EA Montreal; Xbox 360, PS3): congratulatory player-to-player maneuvers No More Heroes (Grasshopper Manufacture; Wii): suggestive waggle-based sword recharging [Do you agree or disagree with these picks? Feel free to comment below. We'll pick the best reader comments on each list for our final retrospective, to debut on Gamasutra close to the holidays.]