Red Star

Red Stars, added in B3313 v0.9, are a newly introduced mechanic to the game and serve as a loose sense of progression the player can achieve through exploring the castle.

Red Star Locations
Note that these locations will likely be changed up in the final release. Also, due to v0.9's unfinished nature, some Red Stars are actually just retextured Yellow Stars and will count as such. Therefore, the star door in Haunted Castle Grounds leading to the ending route, which requires 13 Red Stars to enter, can not be unlocked via normal means.

Red Stars
These Red Stars, when collected, will let Mario and Luigi regain their abilities, and also influence Hard Mode:
 * Bowser in the Dark World (Shoshinkai): Defeat Bowser and collect the Red Star he drops. This is usually the first Red Star that the player is guaranteed to come across.
 * Bowser in the Bully Battlefield: Defeat Bowser.
 * Bowser's Checkered Madness: Defeat Bowser.
 * Bowser in the Dark World (December '95): Defeat Bowser.
 * Bowser in the Sub: Defeat Bowser (appears as a Yellow Star, but counts as a Red one).
 * Captain Fly Guy's Tower: Defeat Captain Fly Guy and collect the Red Star he drops.
 * Floor 2B: There's a Red Star inside a cork box, hidden well within the floor's giant maze.
 * Goomboss' Lair: Defeat Goomboss.
 * Mario's Maze: Once activating the instant warp, you will find a Red Star at the end of the pitch black hallway. You need to evade several deadly faceless Mario clones to get it.
 * Stellar Tower: Collect 8 red coins in the air with the Wing Cap (appears as a Yellow Star, but counts as a Red one).
 * Toad Catacombs: Collect the 5 secrets by desecrating the dead Toads.

Fake Red Stars
These Red Stars count as Yellow Power Stars, and add to the star counter. They do NOT grant the benefits a real Red Star would give.
 * Basement Maze: There's a Red Star hidden inside a "?" Box inside the room full of fake "!" boxes.
 * Bowser's Castle: Talk to the Toad in one of the hallways at night.
 * Bowser's Checkered Madness: Break open the cork box for a Red Star.
 * Bowser in the Airship Cabin: Defeat Bowser.
 * Floor 2B (beta): Talk to the Toad in the room with the fake "!" boxes. You can get another red Star here by breaking one of the real "?" boxes in the room.
 * Ice-Cold Warzone: Collect the Red Star at the top of the mountain.
 * The Star: Collect the 5 Silver Stars on the edges of the big Star.
 * wf.z64: Reach the Star at the top of the tower within 40 seconds to obtain the Red Star.
 * King Whomp's Battle Arena: Defeat King Whomp.

Red Stars

 * Bowser in the Dark World: Defeat Bowser.
 * wf.z64: Reach the Star at the top of the tower within 60 seconds to obtain the Red Star.
 * Floor 2B: In the Floor 3B section (art gallery) There's a Red Star found inside a Cork Box, hidden within the giant maze.
 * Toad Catacombs: Collect the 5 secrets by standing on 5 coffins.
 * Mario's Maze: Run as fast as you can to the star, whilst avoiding the floating Mario clones. (re-textured death 1ups)
 * Ice-Cold Warzone: Get to the top of the mountain whilst avoiding several Water Bombs.
 * Toad's Hedge Maze: Find 8 red coins within the maze, then make your way to the statue for a star.
 * Mr. I's Maze: Collect 5 secrets while avoiding giant eyeballs that kill you in one touch.
 * Aquarium Limbo: Collect 8 red coins in freezing cold water (water that drains health fast and you can't regen in) to collect the star.
 * Imperfect Sanctuary Lobby: Follow Peach's voice saying "Mario!" to a room with a red star and a peach painting.
 * Eel Graveyard: Collect 5 secrets from 5 clams. (pro tip, make sure to check on top of the middle pillar, there's 2 clams that you need up there.)
 * Basement Maze: Navigate the winding maze until you find ? Blocks with the vanilla texture, and look for a yellow beta ? block, the red star is inside.
 * Wonderland Woods: Find 8 red coins whilst avoiding the ominous floating Shadow Mario that crashes your game.

Fake Red Stars

 * Bowser's Castle: Talk to the Toad in one of the hallways at night.

Red Star Effects
As the player collects Red Stars, they will slowly unlock more facets of their moveset.

First Red Star
Before the first Red Star is collected, most extra areas are blocked off and inaccessible:


 * Any doors in the Castle Grounds aside from the ones leading to Beta Lobby A/Beta Lobby E (such as the entrances to Crescent Castle and Toad's Lobby) will not open. The tunnel leading to Dark Hallway also doesn't function.
 * The fountain in Uncanny Courtyard will not warp the player to its windy state, and the entrance to Battle Fort is blocked off.
 * Warping back to the lobby via the pause menu will only send the player to Beta Lobby A.

After the Red Star is collected, the "personalization" is enabled, and the game will open up to the player properly. Additionally, Mario/Luigi will gain the ability to Long Jump as well as Kick Flip (a move which replaces the vanilla game's Slide Kick maneuver). Additionally, Mario's/Luigi's Side Flip will be restored to its original height.

Second Red Star
Upon collecting the second Red Star, more doors within the castle will open up and allow the player entry. Mario/Luigi will also regain the ability to Backflip, Sweep Kick/Breakdance, and crawl.

Third Red Star and Beyond
From this point, the player does not gain any unique abilities or advantages from collecting any more "Real" Red Stars. However, continuing to collect them will influence many of the Hard Mode changes the player might experience. In addition, 13 red stars are required to open the door at the top of the Haunted Castle Grounds and access the Randomized Realm. This is not possible in 0.9 without cheats, as there are only 11 real red stars in the whole game.

Unabandoned
Unabandoned makes several changes to the progression with Red Stars, to make the unlocks more spread out.

First Red Star
Like v0.9, most warps are locked until you obtain your first Red Star. Collecting it will also give you an improved Triple Jump Spin and Side Flip.

Second Red Star
Collecting the Second Red Star reenables the player's Long Jump and also enables Personalization Values.

Third Red Star
Enables the Backflip and Breakdancing.

Fourth Red Star
Enables Night Mode and the Slide Kick.

Fifth Red Star
Enables Soundbank corruptions.

Thirteenth Red Star
Unlocks the door in Haunted Castle Grounds allowing access to Randomized Realm.

Trivia

 * While not particularly relevant to the player unless they happen to sequence break, collecting the first star also enables many of the game's jumpscares and spooky events (as an example, the pipe teleport in Plexal Basement that sends you to the flooded state of the level does not function unless 1 real Red Star has been collected).
 * In 1.0 Unabandoned, the duplicate star IDs and most of the fake red stars were fixed, so it is possible to reach the Randomized Realm and the ending courses. In 0.9 the ending sequence is unavailable due to the lack of red stars.
 * Prior to a more recent version of Unabandoned, one of the Red Stars used to be located in The Star before eventually being moved to wf.z64, likely due to the former being too easy to obtain.