In simple terms, a series. One that has multiple creators, and spans several themes. Currently there are plans for 9 worlds + 1 special world each increasing in elevation- in order they'd be Lava/Fire, Cave/Underground, Water/Beach, Desert/Ruins, Grassland/Plains, Mountain/Snow, Sky, Space, a Fortress world, and then finally the special world.
Castles and Towers have different bosses.
Depending on the format of the final level layout, there is potential for multiple paths that lead to the same endpoint.
Each level would be expected to match the theme of the world fairly well, however, deviance would provide variety on occasion. For example, one could find a grassy oasis in a desert level, a cave in a mountainous region, or even something so audacious as a town in the middle of a grassland. Creativity is an asset, but try to keep them mostly conforming to the theme. In addition, levels should conform to the general style of the
14th LDC (Pure Platformer), that is, a relatively linear path from start to finish. Possible shortcuts (both in the level and to other levels) may be an option, but please keep signs and powerups to a minimum.
Finally, the tenth special world will be an opportunity for all participating designers to make something totally their style, with no set theme. It's a chance to leave your own personal mark on the series so to speak, like a level designing signature. Only one level per user will be allowed in this world, so make it count. Unless those 4 insane guys which are in charge of this now do something else.