Super Mario Flash 2: Cryogenic Edition is the fourth hack created and developed by BrokenAce.
You can play the game here on Level Palace.
Cryogenic Edition is themed after winter-like themes, such as snowy overworlds, ice caves and cold castles (Cryogenic = relating to low temperatures). This was actually requested and wanted by the SMF community for a while, as snow levels are to be found in many of the 2D Mario games, and neither SMF1 nor SMF2 had in-build ice themes (this was even before the Custom Background feature).
Despite being one of the early hacks, the hack still has a good level of quality to this day, despite it being not updated anymore. It also was well praised for, despite the hack just themed around one main theme (winter), it had lots of different sub-themes like snow grasslands and ice caves to work with, still giving some variety.
Launch (2014, Date not known yet)
The official launch for Cryogenic Edition.
Update to SMF2 2.1
When SMF2 2.1 was officially released, the hack was updated shortly after, and also made some big general improvements over a few issues in the original release.