Ajax is really two good games in one. Levels alternate between a very solid vert shooter (with particularly good sound) and a great 3D airplane shooter (over-the-shoulder-space-type).
You start in the vertical shooter mode. You are flying a helicopter and three buttons control your weapons. You have normal fire, bomb, and super bomb. The bomb is for ground targets and has a typical cross-hair that flies at a fixed distance out in front of you so you know when to drop. One little added cool feature is that the cross-hair changes from a plain cross-hair to one with a white circle around it when you are lined up over a target and it is time to bomb. The super-weapon (button 3) blows up most of the screen (not all) but is very limited in quantity and is not often replenished.
There are power-ups when you kill some enemies. In fact, you can tell what they are because they have indicators at the bottom of the screen - better bombs, vulcans, 3-way shot, triple and laser. That's right, 3-way AND triple. As I mentioned above, the sound is exceptional - especially for 1987, Rich bass resonates with each shot, not the tinny little crap sound in many games of the 80s.
The 3D levels (even-numbered levels) are my favorite. They are very well done, The 3D is good and smooth. The battles are busy and balanced. And the graphics are great. In level 2, you find yourself flying straight DOWN thru the clouds toward a fleet of ships. And yet in level 8, you are flying thru space avoiding asteroids and shooting down spaceships. On these levels, you only have two buttons for weapons. Normal fire and missile.
There are other little touches, for instance on the first level, there's a hole blown in a large wall and you have to fly through it - anywhere else and you crash into the wall (you can't fly over it). Of course, all the enemy fire is concentrated in that small space.
In all it's a really great game enhanced by the fact that it's really two very good games in one.
Ajax - simple name, simple design, but all put together very well.