It's not very Well Documented, and I don't even know much about it myself(I just Discovered It Today) So I'd recommend Downloading and giving it a go to understand how versatile it is. So has anyone ever wanted to Edit the health of NPCS? Use Default Graphics with Customs replacing the same NPC? Have More Powerups like the Frog Suit, Tiny Mushroom, Mega Mushroom Or Starman? Lua Scripting functions to control Global variables? Layers and events on the world map? Optional Wall Jumping? SMB3 Style Map Item Inventory? More enemies like Chain Chomps? Or a Functional SMB1 Flagpole? SMBX 1.4 To The Rescue! Seriously this thing is awesome And RMN has been Missing out! A Chinese Coder Named 5438A38A made this from the ground up recreating, and improving upon SMBX! It is even able to convert classic SMBX Levels to the new format, but bit of a warning if you want to convert old levels, there is now a max for resizable Blocks, so If your Level Makes them Giant they might get all messed up when converting. 2020 Update: Since February 2, 2020, the source code of SMBX is now open under MIT license (license file in a repository): Here is a news post about that: SMBX Legacy Source Code Latest Bulletin Currently, there is no stane-alone option for distribution. Levels and episodes made in SMBX require the engine to play. Besides Mario and Luigi, there are also Toad, Princess Peach and Link as playable characters. There are classic power-ups such as the Fire Flower, Tanooki Suit, Yoshi, and Kuribo's Shoe, but also new power-ups like the Ice Flower, The Billy Gun, and the Propeller Block. Custom graphics and custom music can be imported into levels.

The game is playable with a friend in the 2 player co-op mode, where the screen seamlessly splits and combines as the players separate and rejoin. It is possible to create episodes using either the SMB3 or SMW styled world map, or using a Mario 64 style hub level that has the players collect stars to advance. It contains an extensive point-and-click level editor that allows for the creation classic Super Mario Bros. engine project that blends elements from Super Mario 1, 2, 3 and World, with SMB3 physics.

Smbx 1.4.5 smb1 playable character