ZeroRanger takes "love letter" to an extreme conclusion, creating a shmup stuffed with references to other great shmups. It may have some missteps along the way but creates a tight and engaging experience that is well worth playing through.
On an Earth-like planet called Daikon, aliens called Green Orange have invaded to destroy the planet. Two remaining fighters rise up against their planet's hijacked defense force and a fallen fighter in order to destroy the main Green Orange vessel. While I won't spoil the details, there are surface level themes of enlightenment (complete with lotus imagery) and a little bit of time travel along the way. It's not a particularly impressive shmup story and grates with cryptic self-importance but it doesn't interfere with the game's main experience.
The player has access to two types of ships (wide and focused range fire) with three pairs of weapons they can choose from, ranging from back/side fire, charge/lock-on shot, and a special mode that incorporates a sword and drill. While the first two pairs are standard (but helpful!) the sword and drill transforms the character into the game's most unique premise - a close combat action spectacle. There's even the opportunity to map a slow button to help control speed as this game plays very fast and loose.
The game has a checkpoint system that rewards players with practicing/grinding for score, allowing players to make it through on a fair amount of lives. They'll need it, because this game spikes into an insanely hard difficulty near the end that can get pretty frustrating - along with a second loop, there's also a nasty path for a good ending that deletes players' save data (all checkpoints, all that progress) if they fail a deceptively difficult segment. It's not ZeroRanger's best idea and is more aggravating and stressful than groundbreaking.
As for the style, ZeroRanger makes incredible use of pixel art and a limited color palette, with shades of green and orange (along with some other colors later on) throughout. The game struggles a bit with an identity of its own, mostly since its entire style is chock full of references to other games and anime (Gainax mecha, specifically), Expect Evangelion, Kotsujin, Cho Ren Sha, Undertale, and a Gurren Lagann drill along the way. For fans of all these games/series it's a dream come true, but ZeroRanger is a tad bit less memorable than its inspirations.
All things aside, ZeroRanger isn't my favorite shmup but it's a fairly well designed game that caters to fans of the genre and while it's deceptively inaccessible at parts it's well worth a shot if you're up for the challenge and want to spot some references.