Cloud is a third-person computer puzzle game based on weather and atmospheric aesthetics. The game features distinctive hand-drawn art, as well as non-violent, whimsical play inspired by Keita Takahashi's Katamari Damacy.
The object of Cloud varies between the four missions presented in the game. In the early stages, the player is freely allowed to become accustomed to the controls in a type of tutorial. The player experiments with flight, which occurs on a 2D plane. Speed depends on the distance of the cursor from the player's avatar. 3D flight can be attained by holding the 3rd mouse button. There are three types of clouds in Cloud.
Neutral Clouds: Gray in color, these clouds do not respond to the player. If they come into contact with white clouds, they will be purified and turn into white clouds.
White Clouds: White in color, these clouds belong to the player and will follow the player in flight. If the player travels too quickly, however, these clouds will break away from the player's pull. A connection can be reestablished by flying close to the white clouds.
Dark Clouds: Black in color, these clouds can be considered the game's enemies. When the player flies into a collection of black clouds, the player's white clouds will combine with the dark clouds, eliminating both of them and forming rain. Numbers play an important role in this aspect of the gameplay. A large number of white clouds will more easily overpower a small number of dark clouds, and vice versa.
The shift key and left mouse button combination is utilized to gather white clouds inside the player, though there is a limit to this. If the player holds the control key while stationary, a single cloud will form that will increase in height. A short white cloud cannot purify a tall dark cloud, and so the white cloud must be made taller in order to conquer a large dark cloud.
If the control key and left mouse button combination is pressed while moving, individual white clouds will be released one by one along the flight path. This allows the player to draw intricate drawings in the air for both primary mission-based objectives and secondary puzzle levels.