Super Smash Flash 2
There are button commands such as Jump, Up, Left, Down, Right, Dash, Grab, Attack Special, Shield... and all of them can be set to which ever button you want. Just head to the Options menu, select the Controls option and set your commands as you like, which also applies to all 4 players
You use the mouse and drag your player icon to the character that you want to choose, and after everyone has finish choosing their character, press Space to begin the match.
At the end of each match, the game will let you know specific information such as the number of KOs you dealt to your opponents, the amount of damage caused and received, the number of times you dropped off the stage... and tally up the score for each player.
This game also allows you to customize a lot of things before a match like the time limit, stock, damage ratio, item frequency, start damage, the types of items that can appear in the match... and you can pick the Random option when selecting a character or map.