Arcadia is a space shoot 'em up along the lines of Galaxians and Space Invaders. You have a ship at the bottom of the screen. Enemy ships come at you in waves scrolling across the screen from right to left.
There are twelve levels. When the last level has been completed the game cycles to level one again and continues with no increase in difficulty.
You get an extra life if you clear 4 waves. They keep on coming and the object is to get a high score.
Interesting key mapping on this game: the bottom row of keys moves left & right, but they are mapped alternately so Z, C, B, M and SPACE move you right while CAP SHIFT, X, V, N, and SYMBOL SHIFT move you left. The middle row of keys (A, S, D, etc) power the thrusters while the top row (Q, W, E, etc) fire the dual lasers.