This game is defunct. Do note the game no longer works at all without modifications. This is most likely due to the game's servers being shut down (as of March 31, 2021). As a result, further official developments with the game are unlikely to happen.
Super Mario Bros. 35 was a multiplayer Battle Royale released to celebrate the 35th Anniversary of Super Mario Bros., with "35" referring to both the anniversary and (much like Arika's earlier Tetris 99) the fact that each match had a maximum of 35 players.
SMB35 used the levels and audiovisuals of the original title with a few tweaks and twists, the biggest being that defeated enemies were sent to other players (denoted by being in grayscale), which could - and very often did - lead to some crazy scenarios (Bowsers in non-castle levels! Hammer Bros. underwater! Two dozen Lakitus on-screen at once, all throwing Spinies!). To help combat this, players could pay 20 coins to use a Mario Kart-esque item roulette that would give a Super Mushroom, Fire Flower, Starman, or an automatic POW Block. Coins could also be spent before a match to start Mario off in Super, Fire, or invincible form. Plus, no microtransactions!
Unfortunately, looming over all the fun and chaos from the start was a(n inexplicable) built-in six-month lifespan, with the game only being playable through March 31, 2021. The only official explanation ever given for this is that the game was part of the 35th-Anniversary celebrations, though eyebrows were raised further when Pac-Man 99 was released just a week after SMB35 was shut down.
While SMB35 removed the intro sequences for the underground and underwater levels, the music used in those portions was still present in the files, along with a "hurry up" version (in SMB35, the "hurry up" fanfare would sound once there were 5 players remaining, at which point all music played through the end of the match would be the sped-up versions).
Notably, the unused music is stored in sound.fspj (a file used for mainly sound effects) rather than being an audio stream alongside the other background music, and the file names suggest they would have been used when a match was about to start.
In the initial release, Bowsers that were sent by opponents had a weird behavior when they shot their fire at you: their fire always went to the center of the level height, rather than the height they spawned their fire on. This was fixed in v1.0.1.
Initially, if a kicked Koopa shell got stuck between solid blocks with only 1 tile to move in, the shell's "bump" sound played on every frame the shell hit a solid block - and since it got stuck between two solid blocks, the sound played constantly.
v1.0.2 fixed this by adding a delay for when the Koopa shell bump sound could play again.
In the middle of the level is a set of stairs that has a hidden 1-Up Mushroom. SMB35 originally had the stairs one block too short, which also resulted in the hidden block being lower. This was corrected in v1.0.2.
The pair of clouds right before the first pipe has a two-block-wide gap between them. The original game has a one-block-wide gap, which is also the case for the other cloud pairs in SMB1 and SMB35.
The build path suggests that kuku was the game's internal name. In Japanese, this can be read as "99", similar to Tetris 99 and the later Pac-Man 99 and F-Zero 99. Perhaps at one point SMB35 was meant to be a 99-player game?
