Onet Mahjong, also known as Onet Mahjong: Tile Connect and Match, is a connect-style matching game. In a rural village in the mountains, the player removes candy beans, donuts, orange slices, wrapped candies and other sweet treats and everyday items from checkerboards from level to level in pairs. They remove all items or complete tasks. They also earn coins to use to purchase boosters and three stars per level.
The player can only remove items by pairing identical ones using up to three connecting lines that have no more than two right angles. They can remove items along the same edge and side by side or stacked in adjacent positions. They can also remove pairs across gaps at the center of a board or along its edges, as long as the connecting lines rules apply.
The game removes a connected pair. On some levels, it slides the remaining items into new positions. It increasingly makes gameplay difficult by putting obstacles in the player's way, such as chains or ice blocks.
Onet Mahjong counters these difficulties with boosters below the board that become accessible at certain levels. It times play to gauge how many stars to reward the player. As a result, they must move quickly. One of the boosters, a snowflake, can momentarily freeze the timer. The boosters also include a wooden mallet that can remove a single item or obstacle and red arrows that shuffle all the items.
Over time, the game gives the player a gift box based on the number of stars they collect per level. Their coins transfer to a cat money bank that they eventually break. The main screen has a wheel of fortune minigame that offers them a free prize. For additional coins and prizes, they must watch ads.