Namely, everyone is a Space Pirate.
You play as the titular Captain Flinthook, bravest buccaneer in the Mermaidon Galaxy, and former Keeper of the Galactic Lighthouse. For no apparent reason, the entire planetoid said Lighthouse was on has been completely destroyed, scattering the other Keepers across the cosmos and rendering the spaceways completely unsafe for anyone other than skilled pirates. Worse, the notorious Cluster Clan has gotten word of it, and the three captains of the piratical navy have captured three of them in hopes of using their powers for their own gain. It's up to Flinthook to save the other Keepers and bring about a new golden age of space sail — but who's this strange wizard who seems to dog him every step of the way?
Flinthook revolves around two mechanics, namely the Chronobuckle and the Quickshot; the former allows Flinthook to more easily dodge the regular Bullet Hell the Cluster Clan brings to bear, and to pass strange chrono-beams the various ships of the Clan have installed to block any would-be boarder's attempt to take their ships. The other is how Flinthook quickly travels around said ships, using various grapple rings, and how he breaks the Bubble Shield of pirates rendered otherwise invincible.
Flinthook provides examples of:
- Anti-Villain: None of the Cluster captains are particularly bad people — the worst is Bad Billy Bullseye, and he just has a Hair-Trigger Temper eased by his beloved Big Wool. This is probably why Flinthook feels safe getting their help when Gwarlock begins his Keeper absorption scheme.
- Batman Can Breathe in Space: Zigzagged. Flinthook can ride his trademark giant anchor to board ships with no protective equipment, and some of the graphical flairs and designs imply that there is sometimes no glass in the ship windows. However, there is a ship modifier, Asphyxia, that causes you to start taking rapid damage from apparent lack of oxygen if you run out of time.
- Bonus Level: Two types, neither of which has a Ghost Gem needed to find a captain, but useful for the gold and getting the True Ending.
- Nomad's Lands are small planetoids that appear if you've taken minimal damage clearing a couple ships, creating a short level with three chests in its single subarea.
- Ghost Ships manifest if you have three or more curses on you. These are normal big ships, with the exception that every common enemy is a ghost, and there's a true boss at the end. You need to clear all three if you want the true ending, as they have three of the six Keepers aboard.
- Beam Spam: Bad Billy Bullseye shoots his gun faster and faster as he loses health, and he also aims it in your general direction, so it can lead to you getting hit very easily.
- Brain in a Jar: Subvberted; Baron von Guu looks like it, but a look at his lore energy reveals he's actually the slime it's floating in.
- Deal with the Devil: While it's unclear if the creature in Devil's Lodge ships is an actual devil, or a dragon / some other creature, it does give you a tainted offer of power — Take a curse in exchange for money, health and a perk.
- Empty Room Until the Trap: Rumble Rooms. Contains a single guarded chest, and if you talk to the person sitting on it, they let you have the chest...if you survive the waves of enemies they summon.
- Flunky Boss: Two of them - Bad-Eye Billy and Gwarlock. The former's mount spawns eggs that split into two Starfish, which can easily overwhelm you if you don't keep them in check. The first half of the latter's fight revolves entirely around summoning waves of Ghost enemies. The sheer amount of them per summon and the fact it's 16 waves make this a grueling test of endurance.
- Interchangeable Antimatter Keys: Present and accounted for, though only apparent in ships under Lockdown, as most ships only have one key and one locked door.
- Invincible Minor Minion: Purple Ghosts and the Crusher variety of pirates.
- Multiple Endings: Two of them:
- The Normal Ending; You defeat Gwarlock, but without the power of all six other Keepers, he just dies, and the Lighthouse is still destroyed.
- The True Ending; With all six Keepers, Gwarlock is turned back to normal from his One-Winged Angel form and his magic is used to restore the Lighthouse, which is what he really wanted. He and Flinthook make amends and go off adventuring with the Cluster Clan.
- Power at a Price: All of the Curses. They all affect you negatively in some way, but they all increase the XP you earn as a tradeoff.
- Science Fantasy: Pirate mages aren't an uncommon sight, there's frequent attacks by ghostly undead pirates, and the main antagoinst, Gwarlock, is a literal wizard in traditional apparel.
- Shoot the Medic First: Strictly enforced with the bubble mages — They render everyone invulnerable until they are taken care of.
- Triumphant Reprise: The final boss theme is a combination of both a frantic, up-tempo version of the Title/Intro theme and the boss's first phase, which is in itself a remix of the Tutorial music.
- We Used to Be Friends: Gwarlock and Flinthook used to be adventuring partners before the former became obsessed with power and fame.