On the list of games that should never have been tried on the 2600, Tempest has to be near the top. Why Atari decided they could reproduce a 3D vector game on the 2600 is beyond me, but the results were disastrous. Thankfully Atari killed off this experiment gone wrong before it could hurt anybody.
I've said it once and I'll say it again; If there's one thing the 2600 doesn't do it's diagonals. Unfortunately Tempest is chockfull of diagonals as the tubes angle out from the center of the screen to form complex geometric patterns. This leads us to the next problem, if there's a second thing the 2600 doesn't do it's complex geometric patterns! The 2600 version gets around this by not having 3D tubes, but rather a flat looking shape with the enemies coming from one side and the player moving on the other. For some reason the "shape" seems to flux and change a bit as things move around the screen, this is probably the result of a programming glitch. The "shape" is segmented into what could be called tubes (if you use your imagination), but these "tubes" don't seem to correspond to where the real tubes (which are invisible) are.
This brings us to the next problem, if there's a third thing the 2600 doesn't do it's 3D perspective. Atari couldn't get around this one; the 3D perspective is what makes Tempest "Tempest". Atari tried to simulate this by changing the enemy's size to make it look like it was getting closer. Unfortunately there aren't nearly enough frames of animation to do this, so the enemies sort of jump forward in an awkward fashion. The enemy graphics are very blocky and becomes even more evident as the size is increased when they approach the outer edge of the tube. This combined with a very blocky looking "shape" for the board makes for one nasty looking game.
Amazingly there are four different types of enemies present in this version.
The controls in this early version are very frustrating. There appear to be set places where your blaster can move to (hidden tubes), but they don't seem to correspond to the shape on the screen. This wouldn't be so bad if they were at regular intervals, but they seem to be very close together towards the middle of the screen and very far apart near the edges. This makes lining up your shots with the incoming enemies very difficult because you're not quite sure where the next "hidden tube" is. This coupled with the fact that the "jumping" enemies move very quickly up the short "tubes" makes for a very difficult game. The firing is a bit off as well, and it appears that your blaster will fire towards the left side of it's graphic instead of from the middle. This wouldn't be so bad if the bullets didn't have a bad habit of disappearing when too many object are on the screen (probably due to flicker), this can lead to some mysterious deaths from invisible bullets. Thankfully you have your Super Zapper in this version, which can be activated by pressing up and fire.
In the programmers defense, they did a wonderful job on Tempest considering they were asked to do the impossible. Since this version isn't complete, it's really not fair to start judging it yet. Given some time, I'm sure a much more playable version with improved graphics and smother gameplay could have been put together. While it probably wouldn't have ever looked like its arcade counterpart, this prototype proves that Tempest could (in a very limited fashion) be done on the 2600. A later version with some added features like a title screen was reviewed in Ultimate Gamer magazine, but it's unknown what happened to that prototype.