In the test mode, you can zero the high score table and examine the game parameters, but not modify them. Scores beyond 999999 are not possible, as the score will roll-over to 000000. There was a Major Havoc conversion kit made for Tempest machines that included its own unique control panel, sideart, decals and marquee. Tempest Tubes is a ROM upgrade created by a hobbiest that contains totally different and more difficult tube shapes. The shapes vary from a line, to a triangle, to a circle, to more complex shapes.
Enemies enter from the bottom and work their way up towards the top.
Collision with an enemy or an enemy's shot is fatal. A level is cleared when all the enemies have been destroyed, or the only enemies left are the red shooters that have reached the top of the tunnel. When proceeding to the next level, shoot and destroy, or avoid, the green spikes that are left over, as a collision with them is fatal. The superzapper will destroy all the enemies on screen the first time it is used. The second time has a much more limited effect.