Raptor

Raptor: Call of the Shadows is a 2D vertical-scroller single player game developed by Cygnus Studios and published by Apogee Software. Its working title was "Mercenary 2029". It was released on April 1, 1994 for DOS. The game is divided into three "sectors": Bravo Sector, Tango Sector, and Outer Regions, all of which have nine sub-missions called "waves", making for a total of 27 levels (9 per sector). The full version of Raptor allows players to start out in any of the three campaigns, though playing them in order helps the player to more easily accumulate money for weapon and shield upgrades. Once a player beats a sector, they can replay it with all the money and weapons that they have accumulated. The difficulty is increased when the player does this however, e.g. if the player beats the sector on Rookie and replays it, the difficulty will be set to Veteran.