According to Ubisoft Singapore Design Director Julian Koh, Assassin's Creed Black Flag Resynced is being created "from the ground up" and will be "a love letter to the original."
In an interview with GamesRadar, Koh explained that the team was forced to rework many gameplay elements due to new mechanics and modern graphics. In particular, changes affected the parkour system, collisions, and environment.
The size of objects had to be changed due to the ability to crouch and a new level of detail. Parkour also had to adapt, so we are redoing the collision system. The core gameplay remains the same, but now we have many more tools. The game had to be completely rebuilt from scratch.
At the same time, the authors emphasize that they are trying to preserve the spirit of the original Assassin's Creed IV: Black Flag. Creative Director Paul Fu stated that the project will remain "a classic old-school Assassin's Creed."