Marky Mark is a game for at least 2 people, at least of whom is the Game Master.
The only required equipment is a tool or set of tools that leave marks (markers) and something(s) that can be marked (blank white t-shirt).
The Game Master (GM) decides where to place the t-shirt, how to distribute the markers, when the game starts, the boundaries of the game, how long the game lasts, what the win conditions for the game are, and any other rules/limitations of the game.
To Play:
Players decide who the GM will be.
The GM indicates where the shirt will be.
The GM distributes the markers to the players or places the markers somewhere.
The GM tells the players what the game objective(s) is either publicly (out loud) or secretly (using hand written objectives that are either given to specific players or assigned randomly).
The GM indicates if the game ends after one player completes their objective(s) or if multiple players can win.
The GM indicates the boundaries of the game.
The GM indicates how long the game will last.
The GM indicates where the players will start, and how much time before the game begins.
Someone starts the timer, and the GM announces the start of the game.
The GM can change the rules at any time.
Players are allowed to use any technique to complete their objective so long as the GM has not outlawed it.