This could be hard.What old game is this? I don't know when it was released but, I guessthink it iswas released after 1990 (Not 3D). It is a Platformer. I believe it is about aliens All I can remember is that in.
In the first level you arrive in a car and there are these skeletons and you shoot them. As you keep on walking there are buildings (or lifts) that you can use. There are collectible crystal shards. After some levels you will find a big skeleton monster in a room. Another level I remember is -has you are on the top of a building and something someone/someone is firing rockets at you. Anyway there
There was skeletons in most of the levels and they looked alien. I doubt the name of the game started with B- . Even though it was 90's game I played it on Windows XP
EDIT -. It is most probably a DOS game. It is similar to Dangerous Dave 2Dangerous Dave 2