Tempest
1980
Designed by Dave Theurer

Tempest is abstract even by Atari standards. Each level is a one-screen web, divided into lanes. The player can move around freely along the outside of the web using a dial, but his position always resolves into being in one of the web's lanes, and shots always travel down the center of a lane.

The web is in perspective, with the player's movement area being at the close end, and the center of the web in the distance. This is where the enemies come from, and clearing a level means destroying all the major enemies on the web.

The primary enemy is the Flipper, a tie-shaped thing that sails out from the distant center of the web towards the rim where the player resides. One shot kills a Flipper, but there's many of them and they're pretty quick, and the player must try to shoot them before they make it to the end.

If a Flipper makes it, it "flips" along the outside of the web, out of the player's reach, and tries to "capture" him by flipping behind him and taking him in, which costs him a life. Flippers on the outside can be killed either with the Superzapper or by shooting just as the Flipper's about to hit the player.

The most interesting "enemy" are the Spikes. They don't directly attack the player; in fact, they don't move at all. They start each level on the board, protruding into the lanes of the web from the distant opening. If a shot traveling down a lane hits one, it "pounds" the Spike back a bit, the amount varying according to the level, and a Spike pounded all the way back vanishes.

While they may block shots meant for more aggressive foes, they aren't dangerous until the level is complete. When cleared, the player sails down and through the web, with a 3D effect, to reach the next level. Any Spikes left during the level remain during this sequence, and if the player hits one along the way he loses a life and is sent back into the previous level.

The player can still move and shoot during the exit animation, so the can try to dodge into empty lanes and pound short ones down while exiting, but it's usually better to make sure there are free lanes available when the last enemy is killed... which means there are actually times when it's best not to kill that last foe. One of the enemies, Spikers, has as its purpose in life the growing of Spikes.

Tempest is one of the twitchiest games ever made, requiring total concentration to survive later waves. Most twitch games ultimately use a joystick, sometimes two, because of their familiarity to the player. Player movement in Tempest, however, is ultimately one-dimensional. The player movement zone during each wave is the outside of the web only.

Since dials are a very analog form of control, the game can throw situations at the player requiring speed and precision where ordinary digital movement would be inadequate, and indirectly helps take the rough edges off the design. If the player's lane is surrounded by enemies he can still escape if he can only twist the knob fast enough, while if he had a constant travel rate there would be more situations that come down to being inescapable.

Link: Interview with the designer of Tempest (unnamed, but obviously Theurer).