Arcadia was a two-dimensional shoot 'em up released in time for Christmas 1982 on the Sinclair Spectrum and Vic 20 platforms.
Published by Imagine Software, Arcadia was a Space Invaders fixed shooter that also took elements of Gorf and Galaxians to create a simple - yet for its time - fast action game. The player controlled a space ship as the aliens scrolled and moved freely down the screen. The game consisted of 8 different levels of descending aliens. After level 8 the game looped back to level 1 with no extra difficulty. An extra life was rewarded after every four levels.
Arcadia was well received by the review magazine of the time - ZX Computing said it was "highly addictive and well presented", Computer & Video Games said "it lives up to the advertisement blurb and gives you a good addictive game of Space Attack" - rating it 8 out of 10. Home computing weekly agreed, stating it was "well packaged and well worth the money", rating it 86%.
The ZX version was written to be compatible with the Fuller Sound Box - which included a joystick port. If the box was not connected the nonexistent port was read incorrectly making the space ship occasionally fire of its own free will. This was potentially hazardous on some screens - such as level 4 "The Pins" - where it was tactically sound to leave a single pin falling rather than shoot it and have an entire squadron descend on the player again.
Source: Wikipedia, "Arcadia (video game)," available under the CC-BY-SA License.