Tac/Scan

Tac/Scan is a three-dimensional shooter arcade game that was released by Sega, in 1982; it runs on their G80 Vector hardware, and was their only vector game to use a vertical monitor. The player must use a rotary controller to guide a fleet of seven ships through three different stages - Armada Attack, 3-D Armada Attack and Space Warp Tunnel, which will get killed if they are shot, fly into an enemy, or fly into the sides of the tunnel in the third stage, but you can earn them back as the game goes on. When the Firing Button is pressed, all seven ships will fire simultaneously; when the Add Ship button is pressed, one of your remaining ships will be added to an empty position in the formation. Where it will end up is indicated by a ship's ghost image that will always be moving over the empty positions - so you will have to time your button presses accurately to add a ship where you want it, and if all the positions in the formation become empty, your game will immediately finish, regardless of how many ships you have remaining. There is also another way to add ships to the formation; during gameplay, friendly ships (that cannot be killed by your shots), will fly into view from the left and right sides of the screen and mingle with the enemy ships, and you can direct them into the empty formation positions. Also, if you direct one of them into the position at the front of the formation, it will cause the formation to rearrange itself - and, if you direct one of them into an already-filled position in the formation, it will cause the number of remaining ships to increase by one, but you will also receive an extra remaining ship after every 30000 points (by default). Once you clear the third stage, the gameplay will alternate between the first and second stages in a repeating loop (at higher difficulty) until you run out of ships.