The player picks a character to play (in Katamari Damacy you play as the Prince, but in other versions of the franchise you can play as a Cousin) and a level to complete. There are many different level, each with their own objective. You rolls the katamari around houses, buildings, gardens, towns, and cities in order to complete the parameters set by the King of All Cosmos. The player uses the two analog sticks in tandem on the DualShock controller (pictured right) to control the direction the katamari rolls (this applies in the versions of game that appear on the Playstation). Press both pads forward and the ball rolls forward. Pull them back and the ball rolls back. Pushing one pad forward and the other back turns the ball. The right thumbpad also controls the camera. Other controls can be triggered by the player to gain a quick burst of speed, flip the Prince to the other side of the katamari, and more.
Most levels begin with the king demanding a ball measuring a certain size. You then go out and have a specified amount of time to gather enough stuff to make your quota. Inherently, the game measures objects that are smaller than the katamari and allows them to stick to it when the player rolls over them. The game tracks the size and weight of objects and makes anything larger than the katamari cuase collisions which can cause objects to fall off the katamari, making the player pick everything back up. The game also calculates surface area and adds it to the mix of objects to pick up. This allows long, thin objects, such as pencils, that are larger than the katamari, to be picked up, and they will alter how the katamari rolls (at weird angles as if in real life) until more objects are picked up. Large animals, such as cows, will chase the katamari, knocking things from it, but once the katamari is large enough, it will scare the animals away, and they can be rolled up once they are chased down (see example above and left). As objects stick to the katamari, the katamari will grow, eventually allowing objects that were once obstacles to be picked up, and creating access to areas that were previously blocked. In this manner, the player might start the game by picking up thumbtacks and ants, and slowly work up to the point where the katamari is picking up buildings, mountains and clouds. Although the game is quite easy to play, not meeting the criteria set by the King of All Cosmos can be heart-wrenching (see lower right).
A typical level consists of instructions given by the King of All Cosmos to "Make a Star," in which the player needs to grow the katamari to a specific size within a given amount of time. There are other missions that include specific object rules, such as collecting as many items (swans, crabs, pairs) within a given amount of time, or collecting the largest item possible (such as a cow or bear). There is also the option of a "score attack” for any level, once unlocked, in which they can try to make the largest katamari possible in the time allotted. Certain levels can unlock an "eternal mode" by creating a katamari double the goal size. In eternal modes, the player can explore the level with no time limit.
Each level features two secret items that can be found. The first secret item is called a "royal present" which is typically an object that the Prince can wear (see below right in which the Prince is wearing armor and a hat). Most gifts are non-functional costume pieces, but one includes a camera that can be used to take in-game screenshots. The other secret item is a “cousin” of the Prince, which, once rolled up in main gameplay, can be used as a character in the various multiplayer modes. The game also saves and organizes objects the player has collected over time, allowing them to review all the various objects within the game in a special screen on the home screen of the game.
In the two-player mode, a player can choose to play as either the Prince or one of the Cousins. The screen is split vertically; player one is on the left, and player two is on the right. Players compete simultaneously in a small arena to collect the most objects within three minutes. The playfield is replenished with new objects periodically. Players can ram into each other, knocking items from their opponents' katamaris, and if one player leads by a fair amount, then it is possible to roll up the opponent's katamari.
