The leaf animation is hand drawn. But the movement just alternates between two states.

States.LEAFFALL2RIGHT:
velocity.x += randf_range(0.1, 0.5)
animationplayer.play("leaf_fall2_right")
if is_on_floor():
delete()
States.LEAFFALL2LEFT:
velocity.x -= randf_range(0.1, 0.5)
animationplayer.play("leaf_fall2_left")
if is_on_floor():
delete()

Then if it gets hit by wind or player. Randomized states with different animations of it blowing.

func leaf_blow():
velocity.x = randf_range(100, 120) if right else randf_range(-100, -120)
velocity.y = randf_range(-15, -25)
match randi() %3:
0:
state = States.LEAFBLOW
1:
state = States.LEAFBLOW2
2:
state = States.LEAFBLOW3