Surprisingly fun for a game where you basically run around spamming the 🔳 button, though I'm not sure I could recommend it. Missions are comprised of corridors and arenas, sometimes separated by keys that you obtain from slaying all of the enemies in a given location. Unfortunately, the only deviation you'll encounter is how many keys you need to open a given door.

As for the enemies, they tend to walk slowly towards you and occasionally attack, offering little in the way of threat or variety, especially as a ranged class. Enemy placement isn't taken into account either, spawning in waves that appear out of thin air. But what's truly jarring is that there is no way to block or dodge them, it's determined by a stat automatically, so strafing is your best friend. Not to mention, you'll get plenty of healing items and up to 3 companions to deal with them, (though they aren't much brighter). Your party tends to follow close and won't attack if you're too far away from an enemy, they aren't good about casting spells either.

Customization is where the game really shines, as there's a surprising amount of weapons, classes, and outfits to choose from, as well as attachments and upgrades to make weapons behave a certain way. Last of all, the story is simply not worth mentioning, you're tasked with eliminating remnant SEED and run into a mysterious woman over and over again along the way. Surprisingly, the voice acting is incredibly well executed.

Phantasy Star Portable 2 is better, one might as well skip this. But if you do go for it, just two warnings.

1) Being that this is a direct sequel to Universe, to the point that it feels like a downgraded port slash content pack, this game uses that game's PP system wherein PP is tied to your weapon rather than your character. It's a strange way to do it since it applies to spells and melee weapons too, not just ranged weapons, but I nonetheless found it very fun. You will find yourself constantly cycling through weapons as they're depleted and using PP replenishing items heavily, which kinda made me feel like a gun toting badass, burning through ammo magazines as I was mowing down enemies. In fact I grew to like it so much that I was kind of disappointed to see it was changed in Phantasy Star Portable 2, but that game's system admittedly does make more sense.

2) There is no longer a protagonist a la Ethan from Universe, instead you get to make your own character who never speaks and is never shown outside of gameplay (which, once again, was something I found disappointing at first but admittedly makes a lot more sense for a game of this sort) and the story is instead centered on your partner character who in effect becomes the face of the game. This is not in itself a problem except that here the partner has the cringiest voicework in existence. (Her design is also laughably ugly) The story really banks on you feeling empathy for this character, so it is not a good thing. Granted, there are people who find the partner character in the sequel annoying but I found her to be a massive improvement and found the story in the sequel to be a lot better.

I'm starting to get back into the Phantasy Star games because of the whole look and (sort of) simplicity that I would want in an action RPG, and this feels like a good start to just play on a portable device! As it's understandable that most of the dialogue and cutscenes are pre-rendered due to the limited hardware, I still get a decent plot experience out of it. Missions are pretty simple so far as it is the loop of "kill enemies, move on" or the variety being "kill enemies, get key, unlock gate, move on". Hope I won't get too bored :)
Update: I got bored of it ngl