Tempest is an arcade game by Atari Inc., originally designed and programmed by David Theurer. Released in October, 1981, it was fairly popular and had several ports and sequels. The game is also notable for being the first video game with a selectable level of difficulty (determined by the initial starting level). The game is a tube shooter, a type of shoot 'em up where the environment is fixed, but is viewed from a three-dimensional perspective. The object of Tempest is to survive as long as possible and score as many points as possible by clearing levels of enemies.

The player controls a claw-shaped spaceship that crawls along the near edge of the playfield, moving from segment to segment. This ship can rapid-fire shots down the tube, destroying any enemies within the same segment, and is also equipped with a Superzapper, which destroys all enemies currently on the playfield once per level. (A second use of the Superzapper in a level destroys one random enemy.) (Wikipedia)

Unlockables

Achievements

Complete each achievement to get the allotted gamerscore.

Deflect (15) - Clear the first 9 waves without anything reaching the rim in Evolved game on Normal difficulty.

Deplete (15) - Clear wave 5 without leaving any Spikes in Evolved game on Normal difficulty.

Dodge (15) - Destroy 20 Flippers on the outer rim in 1 wave in Evolved game on Normal difficulty.

Flicker (15) - Destroy a Pulsar in Evolved game on Normal difficulty.

Maniac (20) - Score 100,000 points in Evolved game in Throttle Monkey mode.

Secure (20) - Have 5 lives in hand in Evolved game on Normal difficulty.

Shimmer (20) - Reach the yellow waves in Evolved game on Normal difficulty.

Snap (10) - Clear the first 9 waves in Evolved game on Normal difficulty.

Streak (10) - Clear the first 5 waves in 90 seconds in Evolved game on Normal difficulty.

Struggle (20) - Clear the first 12 waves without using a Super Zapper in Evolved game on Normal difficulty.

Trace (15) - Destroy 20 Fuseballs in 1 game in Evolved game on Normal difficulty.

Turmoil (25) - Reach the random waves in Evolved game on Normal difficulty.

One of the older versions of the game, but still a decent one: