Progressively interrupt the jump in the 2D platformer demo

This feels more smooth while still giving a sense of control to
the player.

2d/platformer/src/Actors/Player.gd

@@ -94,7 +94,9 @@ func calculate_move_velocity(
 	if direction.y != 0.0:
 		velocity.y = speed.y * direction.y
 	if is_jump_interrupted:
-		velocity.y = 0.0
+		# Decrease the Y velocity by multiplying it, but don't set it to 0
+		# as to not be too abrupt.
+		velocity.y *= 0.6
 	return velocity