The creators of Tag describe it as "a first-person puzzle platformer which focuses on the players’ ability to modify their environment as they see fit, simply by painting it." They encourage players to enjoy "the endless supply of paint and all the power that comes with it" while traversing each level.
The player is tasked with maneuvering through greyscale cityscapes, which serve as platform-orientated puzzles. To solve each puzzle, the player must use a paint gun that has the capacity for an unlimited quantity of three types of unique surface-altering paint. However, the cans for each paint type must be located in the level before the player can use that particular color. The earliest to be accessed is the green paint, which allows players to jump on horizontal, or bounce off vertical, surfaces. The second paint, red, causes the player to rapidly gain momentum. Blue paint, the final type, enables the player to walk on any surface, regardless of whether it is a vertical plane or ceiling.