Adventure

Adventure mode is a single-player mode in Super Smash Flash, along with Classic mode and All-Star mode. This mode is very similar to the Classic mode, though it includes platforming segments between each of the fights. Though an Adventure mode was confirmed to appear in Super Smash Flash 2, there are very little information besides some outdated posts that appeared on early Smash Flash DOJO!!! pages.

In Super Smash Flash 2
It was initially confirmed that Super Smash Flash 2, like Super Smash Flash, would include an Adventure Mode based on Super Smash Bros. Melee. According to the DOJO!!! update, each level or world is represented as a mini-planet themed with an associated SSF2-in game universe, such as a Mushroom Kingdom mini-planet from the Mario series. With that being said, this information is outdated, so it may not reflect what actually appears in the final game.

Trivia

 * There are unused hidden file for Adventure mode in SSF2 as of v0.9b that cannot be accessed.