* SugarWiki/AwesomeMusic: Practically the entire soundtrack, though the boss {{Leitmotif}} "[[https://www.youtube.com/watch?v=rpKZCg22pXA Butsutekkai]]" is the one most people fondly remember.
* BreatherLevel: Chapter 5 "Metempsychosis" is substantially easier than the previous two chapters and has extremely simple chains. Even the {{Fake Ultimate Mook}}s that appear before the boss firing massive bullet storms only fire in one color, allowing players to easily build up the HomingLaser attack to finish them off. Of course, this is simply to give players time to relax before the sequentially-tiered FinalBoss.
* BrokenBase: All ports of the game after the [=GameCube=] port, including the Xbox Live Arcade, Steam, and [=NESiCA=]×Live ports. Many enjoy these versions for keeping the game easy to buy or play without having to spend a fortune while giving the game an HD facelift. Some top-level players, however, have a hard time enjoying them due to [[DamnYouMuscleMemory the altered chain patterns]], while others are disappointed that [[UnderusedGameMechanic they lack the Conquest Mode that the GameCube port has]].
* CatharsisFactor:
** Chapter 5, the BreatherLevel. Enjoy your constant [[ScoringPoints MAX]] [[SugarWiki/MostWonderfulSound CHAIN]]s before you take on the final bosses.
** Alternatively, ''VideoGame/RadiantSilvergun'' players will find therapy in [[spoiler: [[DidYouJustPunchOutCthulhu DESTROYING]] the [[ArtifactOfDoom Stone-Like]] for good, since it is responsible for both the GroundhogDayLoop and DownerEnding of that game, and finally defeating it [[EarnYourHappyEnding frees humanity]] from the [[EternalRecurrence eternal cycle of destruction and creation]], although the [[TheHeroDies heroes die in the process]]]].
* ContestedSequel: While both this game and its SpiritualPredecessor ''VideoGame/RadiantSilvergun'' are highly-acclaimed, [[BrokenBase some fans tend to argue over which game is better]]. ''Silvergun'' is praised for its complexity and intense storyline while ''Ikaruga'' is lauded for having [[{{Minimalism}} the opposite]]. Understandably, while ''Silvergun'' is a {{darker|AndEdgier}} {{Deconstruction}} of the ShootEmUp genre, ''Ikaruga'' is a [[LighterAndSofter sof]][[SequelDifficultyDrop ter]] {{Reconstruction}}.
* GoodBadBugs: Due to a programming glitch in the Platform/NintendoGameCube port, it's possible to trick the game into giving an extra continue on "[[SelfImposedChallenge No Continue Runs]]" by unplugging the controller from the first slot into the second controller port during the last credit of a continue.
* HilariousInHindsight:
** Another (vastly different) BulletHell game, with a dysfunctional protagonist dealing with the hard times and godly entities throughout the story, and that recognizes {{Pacifist Run}}s for the gameplay? ''VideoGame/{{Undertale}}'' has one, too.
*** Even better, both ''Undertale'' and ''Ikaruga'' can be played on computers via Platform/{{Steam}} services.
*** [[spoiler:The battle with Photoshop Flowey in ''Undertale'' also mirrors that of Stone-Like.]]
*** The exact same thing can be said of the FinalBoss of ''VideoGame/SonicFrontiers''.
** In Stage 4, [[BattleshipRaid the battle against Misago]] has the player(s) attacking its [[ShieldedCoreBoss core's barriers before reaching said core]], just like the core battleships from ''VideoGame/{{Gradius}}''. 3 years later and Treasure developed ''Gradius V'', which even has ''Ikaruga's'' metallic aesthetics and signature boss explosions, along with a cherry-topping of BulletHell.
* ItsHardSoItSucks:
** Its infamous barrier to entry as touted by many reviewers prevents many people who are inexperienced with shmups from looking at this game positively. Not only does this game feature the intimidation factor of BulletHell, but one also needs to constantly switch polarities and thus keep track of two different flavors of bullets to avoid getting blown up spectacularly, something that many gamers feel they lack the coordination for.
** Amongst scoring-minded shmup fans, the game is well-known for how it demands rote memorization to pull off halfway-decent chains and scores, and feels more like a demanding orchestra piece than a game with how a lot of the scoring routes don't seem obvious at first or require some very intensive rehearsal.
* MemeticMutation:
** '''WARNING''': The big enemy is approaching at full throttle. According to the data, it is identified as "Butsutekkai". '''NO REFUGE'''[[labelnote:Explanation]]Rather than the nonsensical BossSubtitles like its [[VideoGame/RadiantSilvergun predecessor]], with the exception of the FinalBoss, this message will always be seen just as the end-level boss appears. {{Irony}} ensues because while players can't avoid fighting the boss (hence "no refuge"), they can deliberately run the timer down to zero, thereby PacifistRun "beating" the boss without destroying it.[[/labelnote]]
** ''Ikaruga'' is a {{puzzle game}}.[[labelnote:Explanation]]Due to the game's chaining system and easier-to-memorize placement of enemies, which involves carefully picking off enemies of the same color, many players joke ''Ikaruga'' feels more like it fits into the PuzzleGame genre rather than the [[ShootEmUp one it's intended to be]].[[/labelnote]]
* SugarWiki/MostWonderfulSound: MAX CHAIN. MAX CHAIN. MAX CHAIN.
* PolishedPort:
** The [=GameCube=] port, [[LateExportForYou which was the first international release]], is best known for adding Conquest Mode, a "practice parts of the stage" mode that also comes with replays showing optimal ways to tackle each section, something [[UnderusedGameMechanic exclusive to this port]]. Perhaps because of this, it is the most favored version of the game by enthusiasts. Arcade purists praise the 'Cube port for the ability to play the game in Tate Mode for the legitimate Portrait screen orientation without letterboxing, as well as the extremely optimized code that removes some of the lag present in the arcade original.
** The Platform/XboxLiveArcade version gives it a graphical overhaul.
** The PC version on Platform/{{Steam}} restores the original enemy patterns and adds a DoublePlay mode, in a nod to a famous superplay video of someone clearing the game controlling both ships at the same time.
** The Platform/NintendoSwitch and Platform/PlayStation4 versions are based on the Steam version, and additionally the [=PS4=] version can run at up to 4K resolution on a [=PS4=] Pro.
* SequelDifficultySpike: On paper, it seems like it would be easier than its predecessor ''VideoGame/RadiantSilvergun'' due to not requiring learning the game's scoring system to power up your weapons and keep them reasonably-powered relative to the enemies you fight and the chaining system no longer locking you into one color until the boss fight at the end of the current section. However, this game also features noticably more complex bullet patterns, as having two different colors of bullets and two polarities to match each one means you have to keep track of two layers of bullets. Scoring-wise, it's even ''harder'' since enemies are often placed in tricky patterns ''and'' you have to destroy ''all'' of the enemies to achieve a relatively competitive score.
* SpiritualSuccessor:
** To ''VideoGame/RadiantSilvergun''. Tageri's very definitely final form, and [[AllThereInTheManual what happened to those who came across it]], is extremely similar to what happened to the researchers in ''Silvergun''.
** It's also a game about switching between two different {{stances|Ystem}}, making enemies of the opposite stance take more damage, similar to the earlier Treasure-created ''VideoGame/SilhouetteMirage''.
* ThatOneBoss:
** The [[https://www.youtube.com/watch?v=F159RI4QK3Q Chapter 4 boss]] due to a claustrophobic "arena" with little moving space for players, all the while the edge of the "arena" fires beams of opposing black/white colors to deter movement and/or force players to take a misstep into one of the beams that will likely destroy their fighter. In order to attack the core, players must shoot down the "gates" leading to the core (of opposing colors, again). Note that throughout the fight the core is rotating, forcing players to rotate along with it, lest they hit the corridor leading to the core. After the first rotation or so, the core fires a laser down the corridor where players are (assuming players have opened all corridor "gates", making the core vulnerable), and since enemy lasers push back the fighter, it becomes another obstacle for players to ensure the fighter stays within the confines of the corridor without hitting the sides that could lead to the loss of life.
** Similarly, first-time players might be slightly overwhelmed by the Chapter 3 boss, though this is mitigated by the fact the boss only fires lasers once half of the turrets that comprise the boss are destroyed. This can be easily circumvented by destroying all turrets of one color first, allowing players to concentrate on navigating through the small "gates" that are rotating in the "arena", since they can have their fighter stay in the same color polarity as the remaining same-colored turrets and absorb their fire.
* ThatOneLevel:
** Chapter 3, "Faith", is arguably the hardest of the game, not just the chaining, but the way the level speeds up through so many obstacles for you to avoid, putting the Speed Zones from ''VideoGame/{{Gradius}}'' or the Turbo Tunnel from ''VideoGame/{{Battletoads}}'' to shame, not helped by the fact that if you play on Hard mode, enemies will return fire, making things even harder to dodge. And then there's ThatOneBoss.
** Chapter 4 "Reality", though from a scoring run perspective. Not only is the environment an obstacle (at least in the first third of it), but high scorers must carefully navigate through this BattleshipRaid level to destroy the appropriate colored enemies and earn consecutive chains. Meanwhile, the chains don't stop counting during the mini-sections where the turrets are firing, forcing players to place their shots carefully to ensure their chains don't get cut for misfires.
* ThatOneRule: The color-chaining mechanic from ''VideoGame/RadiantSilvergun'' returns (shoot three enemies of the same color and get a bonus, repeat successive times without shooting an incorrect enemy to get increasing bonuses), with all the complex chaining routes that entail. This time, you can switch colors between chains rather than being locked into only shooting enemies of one color, ''but'' that also means you have to chain most of the enemies to get a good score now. Fortunately this time, weapon power is not tied to score and the only benefit of chaining is earning a couple of extra lives, so the player can choose how much or how little they want to engage with the chaining system.
* TheyChangedItNowItSucks: Two of the common complaints with the Xbox Live Arcade port are the altering of enemy patterns, [[DamnYouMuscleMemory which can screw up players who are used to the old ones]], as well as [[UnderusedGameMechanic not bringing back Conquest Mode from the GameCube port]]. Furthermore, all subsequent ports use the XBLA port as a basis, rather than any prior version of the game. Yes, even the Nintendo Switch port, which one would expect to be based off the GC version given the company that made both systems.
* UnderusedGameMechanic: Conquest Mode, a practice mode that lets you play stage segments one at a time instead of starting from the beginning of the stage, slow down the game to refine strategies, and watch strategy-oriented replays, was added as part of the [=GameCube=] port, but was not brought back for subsequent consumer versions, all of which use the Xbox 360 port as the basis for the code. This is one of the reasons the [=GameCube=] version is most sought-after by hardcore players.
* WhatDoYouMeanItsNotSymbolic: The chapter titles - "Ideal", "Trial", "Faith", "Reality", and "Metempsychosis" - represent man's struggle towards enlightenment, with the aura-enveloped Ikaruga and Ginkei symbolizing the human soul.