The level was designed by Shigeru Miyamoto to be a tutorial for new players, orienting them to platform jumping and to the rest of the game.
[1] Miyamoto explained that he designed World 1-1 to contain everything players need to "gradually and naturally understand what they're doing", to be able to play more freely, so that it becomes "their game".
Furthermore, Miyamoto ensured that some pits in World 1-1 have floors and can be simply jumped out of, instead of killing Mario and forcing a replay of the entire level.
[2] World 1-1 includes a few secrets that players can discover by replaying, such as a pipe leading to a bonus room and a hidden block containing a 1-up.
[1] World 1-1 has been cited as one of the most iconic video game levels, described by Chris Kerr of Gamasutra as "legendary".
[7] Jeremy Parish of 1UP.com stated that "much of the game's success arose from the fact that it equipped players with the tools to master it from the very beginning."