SUPER MARIO BROS. X
Super Mario Bros. X (SMBX) is a homebrew Mario Bros. engine project that blends elements from Super Mario 1, 2, 3 and World, with SMB3 physics. It contains an extensive point-and-click level editor that allows for the creation classic Super Mario Bros. styled levels. 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. 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. Custom graphics and custom music can be imported into levels.
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. Besides Mario and Luigi, there are also Toad, Princess Peach and Link as playable characters.
Levels and episodes made in SMBX require the engine to play. Currently, there is no stane-alone option for distribution. SMBX is coded in Visual Basic.
A download link for the original SMBX version 1.3 is provided here, while the official website contains links to various newer forked versions developed by the community.
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