Sea Wolf

Prior to Space Invaders, single-player arcade shooters resembled a carnival shooting gallery, with targets moving horizontally in-and-out of the playing field while the player shoots from below. Examples include Anti-Aircraft and Guided Missile.

Sea Wolf is probably the best of these early shooters, largely because it takes care to balance the various gameplay elements. There are three target speeds, each with its own point value (faster = more points), and two vertical positions for the targets. Mines constantly pass horizontally in front of the targets, occasionally obstructing the player's line of fire.

All of this works in concert to create a fun experience with great replay value. Even my son, who spends most of his gaming time on the PS5, has a blast competing with me for a high score in Sea Wolf.

Its inevitable to compare the two, but this seems like a predecessor to the concept found in invaders. you need to fire missiles at roaming boats and submarines. However, in this one the player isnt in danger, the only way to lose the game is by hitting the time limit. In order to keep the quarters coming though there is a highscore to be chased of course. Relatively impressive for the time, but then again everything that wasnt a Pong clone was impressive for the time.