Multiplayer mode, also referred as Versus mode, VS. Mode or Group, is a game mode in both Super Smash Flash and Super Smash Flash 2 that allows players to engage in battles against other players or computer players under a different variety of settings, either free-for-all or team battles. Before starting a match, players can set the rules for the matches like adjusting the amount of time, the number of stocks for each player, apply handicaps, modify the item frequency, etc.. The level for computer players can also be changed by players.
In Super Smash Flash
Referred to as VS. Mode in the original Super Smash Flash, due to Cleod9's inexperience with Flash at the time and possibly due to space limitations as well, only one mode is featured that being Melee mode, which is simply an standard fighting mode where up to two players can engage in numerous battles, they can also set computer player and adjust their difficulty level and set the match rules at their preference.
In Super Smash Flash 2
Now referred to as Group, the mode is further expanded to feature new game options. Aside the regular Versus mode (the successor to Melee mode), players can also select Special mode, which allows them to apply different modifiers that will somehow affect the course of the match like being giant or small, being able to cancel a successful attack to land a new one, receive damage recoil from the ttack dealt to the opponents, etc. Players can also directly access the rules screen from this menu without having to enter the character selection screen.