Tac/Scan

Origins
Tac/Scan is a shooter video game originally released as an arcade game, and later ported to the Atari 2600. It was also included as an unlockable game in the PlayStation 2 version of the Sega Genesis Collection. It was both developed and published by the Sega Corporation in all versions, except for on the Sega Genesis Collection, which that version was done by Digital Eclipse.

Gameplay
Tac/Scan is a unique game in that the player controls just how many resources (in this case, ships) are put into play. The player starts with seven individual ships in play. Those ships can be lost in any of the three stages by hitting a tunnel, getting shot, or colliding with an enemy, which is the laser-firing Ahmins, which composes the superfleet from the planet of Ahm. The player is able to "collect" and earn these ships back as the game progresses. The player can drop down to one ship in the game, but still have four "back-up" ships. If the player loses the one ship in play however, the game is over. This is different from other games that give the player ships sequentially.

In the first stage, the player pilots their ships through waves of attacking enemies. The player can either fire upon them, or "tac" their ships around them, as when the player moves the controller, all ships will move simultaneously. The second stage is much like the first, except that it is from a 3-D perspective from behind the player's ships. In the third stage, the player pilots his ship down a space warp tunnel, and will lose any ships that touch the side of the tunnel. There are two types of enemy ships: one that fires bombs, and the other is a special ship that appears and shoots a laser with a very long range, which usually only appears once during a wave.

Atari 2600 version
This port was scaled down a bit, as there was only the first wave included in this version, which doesn’t go to the second 3-D area, nor the space tunnel. The player also has only five ships maximum, rather than seven, along with there is also only one type of enemy ship to deal with, as the one with the long range laser does not appear.

At the end of each round, a ship will automatically drop down from the top of the screen to replace a ship that the player lost during a round, which the arcade game did not operate in this way, releasing one or more ships a few times during the first round, and then usually at the end of the second.

Also, the game was a bit unusual with the paddle controllers plugging into the right controller port for some reason, rather than the left (as per usual with pretty much most of the 2600 library).

Links

 * Sega Genesis Collection entry at Wikipedia
 * Review of 2600 version at the video game critic site (D-)