The game contains noticeably more story content than your typical shoot-em-up of the era, with a lengthy opening cutscene that can be viewed before the title screen, and more cutscenes seen after every few levels.
The plot centers around a war between the Earth Federation and a race of hostile aliens, as the Federation forces find themselves outgunned with little choice but to withdraw their remaining ships from the battlefield, having already faced severe losses. Before they get the chance to mobilize the fleet, the aliens capture the Federation's flagship 'Oberon' by warping it into their territory with all the crew inside, including Admiral Ken Cabrock.
Ken's daughter Lucia, a Federation pilot, is beyond distressed by the news of her father's disappearance. She learns of a new starfighter the Federation is developing, the Gleylancer, of which a working prototype has already been made, but by the time it's ready for mass deployment, it may be too late for the flagship's crew. Desperate to save her father at any cost, Lucia hijacks the prototype Gleylancer and sets out alone to fight the alien menace.
The eponymous Gleylancer's main weapons are a pair of Gunner drones, which can be powered up with seven different weapons and aim in multiple directions, letting you shoot down enemies no matter where they attack from. When starting the game and after using a continue, you choose one of seven Mover Systems which determine how the Gunners aim and how you control them.
This game provides examples of:
- Area of Effect: The Spread Ball weapon. While its fire rate leaves much to be desired, each explosive energy ball packs a wallop if aimed correctly.
- Arrange Mode: Modern mode in the 2021 ports allows you to change Mover modes at the press of a button instead of having it fixed for the whole game and assign separate buttons for speeding up and slowing down.
- Attack Drone: The Gleylancer's Gunner drones.
- Continuing is Painful: Not quite as painful as in most similar shooters. You lose your Gunner drones and get sent back to the last checkpoint when you die, but it takes only two power-ups of any kind to get the Gunners up and running again. Using a continue puts you back at the beginning of the stage and resets your score, but you have unlimited continues.
- Earn Your Bad Ending: You get the Bad Ending if Lucia's father's ship gets shot down at the end of stage 10. However, his ship can soak up so many bullets before going down that you'd have to actively try to kill him off.
- Fixed Forward-Facing Weapon: The Gleylancer's main gun always fires forward. With the "Shadow" Mover System, the Gunners will follow the ship's movements in a trail and can be locked into formation, but they can't aim anywhere but straight ahead.
- Harder Than Hard: After beating the game on Hard Mode, you are given a cheat code to unlock Mania Mode with.
- Homing Projectile: The "Search" Mover System allows the Gunners to target enemies on their own. You can't control what they decide to aim at, but you are able to toggle whether they aim independently or target the same enemy.
- Laser Blade: The Saber weapon, that projects a limited-range energy blade from each Gunner. Their below-average reach is made up for by high damage output and being able to block enemy shots.
- Multiple Endings: The game has a good and a bad ending. Which one you get depends on whether you can save Lucia's father's ship from getting shot down in stage 10.
- Spread Shot: The 5-Way weapon, which makes each Gunner fire a spread of five bullets with great coverage but a subpar fire rate.
- Whole-Plot Reference: Unintentional or not, the plot of this game seems very reminiscent of the 1986 film Iron Eagle. A fighter pilot who happens to be the father of the protagonist is missing in action, the military is unable to mount a rescue, and the protagonist takes matters into his/her hands by hijacking a fighter to help save his/her father from the enemy.