Pleiads

Pleiads is an arcade game released in 1981. It was ported to the Atari 2600 and the Arcadia 2001.

Gameplay
Pleiads is a game divided into four missions:

First Mission: to defend Earth against an assault of Martian ships and lander craft that will set up barricades to block your shots. You have some help with a pair of radar dishes that will occasionally fire shots at the aliens, but don't fully count on them. Besides being able to fire, your ship can also warp to another location along the bottom of the screen if needs be.

Second Mission: to destroy saucer-like aliens that will descend upon you. They start off small, but eventually will grow big. You must hit them in the center. Hitting only their wings will wound them temporarily.

Third Mission: to destroy the mothership by damaging their engine vents when they are open. You can also destroy it by destroying all the Martian ships that attack you during this mission. However, the more vents you destroy before the mothership blows up, the more points you will earn.

Fourth Mission: to land on the target at the end of the runway when you return to Earth. You must carefully steer your ship around other ships and avoid crashing either into them or the landing lights. Flags will occasionally pop up on the runway, which you can collect for additional points. A fireworks display will greet you when you reach the target safely.

The four missions repeat themselves and get difficult with every level.