Super Mario developer and producer
Takashi Tezuka returned as a producer for
Wonder. Shiro Mouri, who previously directed
New Super Mario Bros. U Deluxe, returned as director.
Wonder started development in 2019 after the release of
Deluxe, During the initial planning of
Wonder, Mouri desired to recreate the sense of "secrets and mystery" that had been present in the original
Super Mario Bros. for a modern audience. The director aknowledged how after
Super Mario games had been enjoyed by players for many years, "those things have somehow become ordinary". The focus was placed on updating the traditional idea of transporting Mario to different areas of the level using
Warp Pipes, vines, or other means. Tezuka suggested to instead change up the current physical location, and the Wonder Flower, which dramatically alters the current level, was born. In order for all levels in the game to uniquely implement this item, approximately 2,000 ideas for Wonder effects were solicited from every member of the development team. The most viable were prototyped and implemented in the final game. Tezuka acknowledged how some journalists and players claimed that
Super Mario Maker, as a
game creation system, "had eliminated the need" for another 2D
Mario game and conceptualized the game keeping this in mind from the beginning as to make it "completely different from
Super Mario Maker". The development team sought to create "a foundation for future 2D
Mario games" like
New Super Mario Bros. had created as the first 2D
Mario game to use 3D elements in 2006 and wanted to develop "a significant evolution" like it was when it was released. For this, a completely new engine to serve as the base was developed and, in addition to using 3D models, the team wanted to implement more "engaging and functional ways of using 3D models possible with modern technology". Additionally, to balance the gameplay between younger and experienced players,
Wonder was designed to have a sliding difficulty scale, with badges that make the game easier or more challenging, an online mode where players can get assistance, characters with special abilities like immunity to enemy damage, and a non-sequential world map that allows players to optionally skip harder levels. The game was planned to have a live
sports commentary on the player's action. Late in development, this feature was superseded by the
Talking Flowers, who exchange humorous quips with the player during levels, because—in the words of one game designer on the project—the sports commentary was too complex to implement and "something [didn't] feel right" about it. In regards to the online multiplayer component of the game, Mouri was conscious of how in competitive games "more-skilled players can have multiple wins and feel satisfied, while newcomers give up early because they keep losing" while in co-op games "those who aren't skilled at games can drag the team down", and wanted to provide an online gameplay experience "free from those sorts of worries" by creating a "live player shadows" system where players can only do beneficial things to each other and the game can be enjoyed similarly to single player but with the addition of online interaction between players.
Shigeru Miyamoto, creator of the
Mario franchise, had very little involvement in the development of
Wonder. Despite this, as mentioned by Tezuka, Miyamoto gave feedback and suggestions to the developers when he occasionally visited to review the game's development progress. Mouri stated that Miyamoto once said that he disliked the original design and the animations for Mario's elephant form, which helped to modify both aspects for the final result. ==Release==