Super Metroid Redesign by Drewseph rebuilds the entire game: every room in Zebes has been redesigned, new areas added, the world map is substantially larger, and the traversal physics adjusted to require more precise movement than the original.
The original Super Metroid takes around 3 to 4 hours to complete. Redesign extends that to 10 or more hours for a first completion, with a world large enough that keeping mental track of explored areas becomes a real challenge. Boss encounters have been reworked and item placement reconsidered for the new layout.
It is a companion experience to the original rather than a replacement: a different game using the same engine and character, tuned toward players who have already mastered the base game.