MBF21

MBF21 (or unabbreviated to Modder's Best Friend) is a specification and standard specifically aimed at mod authors and mods in general. It builds on top of the possibilities shown in the Boom and MBF source ports. It defines a range of new features that seeks to improve the possibilities possible in levels and mods, to be implemented in various source ports.

MBF21 version 1.0 was finalized on May 30, 2021.

History
The idea behind the MBF21 specification arose from the need for a new complevel originally coined MBF+ by Kraflab in a Doomworld thread titled: "Let's talk about mbf+ / a new complevel".

Highlights
To give a impression of what is possible with the MBF21 specification:
 * Instakill floors
 * Better generalized line scrolling
 * Granular control over monster infighting and projectile/splash damage susceptibility (e.g. you can make barons and knights infight, or make imps immune to cacodemons and barrels, and all sorts of funky combinations)
 * New actor flags, exposing a whole ton of previously-hardcoded actor behaviors (e.g. splash damage immunity and boss death triggers), plus a few new things like ripper projectiles and low gravity
 * Weapon flags, make your weapons silent, customize autoswitch-on-pickup behavior, etc.
 * A proper "ammo per shot" field for all weapons, not just the BFG
 * A lot of new DeHacked codepointers, with up to 8 customizable args. This allows mods to feature custom weapons and monsters easily
 * Bugfixes & compatibility options:
 * Fixes for 3-key doors
 * Working generalized crushers,
 * Ability to disable Boom's pushing-monsters-off-ledges behavior

Supported ports
Support for the MBF21 specification will be implemented in the following source ports:
 * Doom Retro
 * DSDA-Doom (Version 0.19.0 from May 30, 2021 was the first port to officially implement the standard)
 * Eternity Engine
 * Odamex
 * PrBoom+ (UMAPINFO branch by Graf Zahl)
 * Woof!

Additionally, the Ultimate Doom Builder level editor provides support for the MBF21 specification through a optional configuration

Credits
The MBF21 spec was developed in a collaborative effort over the course of 2 months with various members of the community. The core team responsible for the spec included the following members:
 * Alex Mayfield (AlexMax)
 * Max Waine (Altazimuth)
 * Boris Klimeš (dew)
 * Matt Tropiano (MTrop)
 * Paul DeBruyne (skillsaw)
 * Keyboard_Doomer
 * Kraflab
 * Xaser