I have a strange soft spot in my heart for the somewhat janky Iridion 3D. It was one of my earliest GBA games and the first handheld title to really awe me with it's visuals—the pre-rendered backgrounds are still the most striking feature of the game today (especially in motion). Shin'en's shooter aimed to blend Star Fox's 3D perspective with more shmup/STG influences, but it ultimately mutated into an awkward combination of both, serving to showcase how unsuccessful 3D rail shooters can be if handled poorly.
Besides the visuals, the first thing you're likely to notice is how wonky the collision is. Star Fox wisely allows objects and enemies to traverse the foreground (behind the Arwing), giving the player a good handle on the game's perspective, but here you're pretty much a sprite slapped onto the front of the screen. Though your ship appears to take up a small amount of space, it acts more like an interstellar rectangle, as you're likely to notice bullets colliding against your lean wings (or the empty space above them). This can make dodging projectiles quite tricky, as your bulky size negates any mobility you might have (the stage 2 midboss and stage 6 enemies are astoundingly difficult to defeat unscathed). Luckily you'll only suffer one pellet of damage if a purple bullet touches your hitbox, but crash into any solid object and you'll lose five. With only twelve points of health and limited lives for the entire journey, you'll find that an enemy veering into your ship at the start of a level can pretty much end the entire run—it's a frustrating thing that happens a bit too often.
The game thankfully has passwords so it's easy to restart a stage, although the passwords keep your lives and power-ups intact (meaning you can screw yourself over if you're careless). The power-ups are also a little haphazardly implemented, reducing your power when you die and when you switch abilities. This pushes the player to sit on a single power-up and be potentially punished for their choice if the stage doesn't feature their specific weapon. Conflated by the fact that certain power-ups (green, purple) don't fire in a straight line—making it hard to hit certain enemies—I think it's demonstrably clear that the gameplay of Iridion 3D is too imprecise to be considered a good shmup.
Yet despite those detrimental factors, I still contend that the game can be an enjoyable experience. If you strap yourself in knowing that the shooter has its share of gameplay issues, I think the variety and atmosphere it offers overcomes a lot of its failings. Each stage is beautiful and distinct from the one before, containing a series of quirky little challenges. There are some frustrating parts here and there (the entirety of stage 4 is a collision nightmare), but the experience is a cohesive one with a good difficulty curve.
I've said that the visuals are the premier aspect of Iridion 3D, but I would be remiss not to boast that the music is the most phenomenal part of the game. Out of the entire soundtrack there's only one dud (stage 6 boss), the other compositions being extremely catchy and atmospheric. I think this accomplishment is made all the more impressive considering how utterly lackluster the GBA soundchip is, as many good games were a bit stifled by the garbled audio. Shin'en's custom GAX sound engine went a long way in achieving this, although I'd argue that Manfred Linzner is a competent composer as well. Seriously, some songs are pretty amazing.
I tend to visit the clumsy shooter title biennially, tapping into feelings that have long since been overwritten by a multitude of mundane etchings. From the large bosses to the captivating music, I still hold a lot of admiration for Iridion 3D. I can't excuse how poor and repetitive the gameplay can get at times, and I must confess that nostalgia is a significant factor in my enjoyment. Yet I don't think much will change me from looking back on Iridion 3D as a flawed game with a lot of heart.