The alien in a jetpack theme gets taken one step further here in Sentinel. You are an alien with a jetpack and must blast your way around the levels. There is a mini map in which you are represented by the blue dot.

The red dots are the enemies and the which dot indicates which direction you are pointing. All in all it's a quite fun little blaster, but the camera angle when you ascend and descend doesn't give you much advantage over the baddies as you are stuck behind the back of the alien. Enjoy!