The Sturm Gambit, sometimes called Mujannah-Sturm, is a decent line in the Bird’s Opening, as it seems to borrow ideas from other openings that feature the c-pawn advance. For instance, Réti’s Opening 1. ♘f3 d5 2. c4 is very similar in the idea of controlling the center.
In fact, it is not a pure gambit, as Black would be punished if they try to keep the pawn after 1. f4 d5 2. c4 dxc4. Check out the following game that demonstrates the trap:
Please remember that opening a diagonal to a rook in the initial position (corner), before developing the minor pieces, is generally risky because the rook might become trapped due to blocked ranks and files. Which is precisely what happened in this particular opening variant.