Alien Soldier is a bizarre game. It starts with a 4-minute text crawl describing all of its extremely over the top and confusing lore (which is detailed even further in depth in the japanese manual), but the actual game doesn't have a single word of dialogue in it. The character is basically half the screen's height, controls are clunky and a bit unintuitive and despite allegedly having "levels", they're basically 30-second bits of holding right while tapping the shoot button at your leisure, with bosses being the real meat of the game.
There's a method to the madness, though. The game isn't amazing at communicating this to you (Alien Soldier is definitely the sort of game where you'd really need to read the manual, or just look up a guide today), but it's one of the most nuanced and rewarding action games of the era. Every system feeds into another one. At full health, your invincible dash turns into a powerful charge that consumes some health. Double tapping the attack button lets you do a short range attack that turns bullets into health, which means that if you play perfectly you can chain the above charge and shred through most bosses. All the weapons serve a purpose, both firing modes have their own uses (you can shoot while moving or standing still, but the former wastes a lot of ammo and isn't always viable, though sometimes necessary), and everything about the gameplay is very carefully considered. I don't know how Treasure did it, but even today Alien Soldier is such a tight and well-realized action game that few can match it.
... At its best, anyways. It is unfortunately marred by a couple of pretty annoying sections, around the mid-late game. There's a couple of stages (read: boss fights) where the environment is completely dark, and you need to fire to briefly light it up. This is hard on the eyes and generally very annoying, but not a big deal. There's a boss battle a bit later on, against a transforming mech, that has five phases, with no checkpoint. No other boss has more than one phase, which makes this by far the hardest fight in the game, even compared to the overall simple final boss. A difficulty spike isn't in itself a horrible thing, but two of the phases use a really annoying, clunky "flying" system where you're constantly wrestling against currents, which takes a lot to learn and shouldn't be something you have to figure out how to wrestle with well into a hard fight. It's way more frustrating than any other part of the game, which overall flows pretty well, and while it doesn't ruin it is is a sore spot. Also, switching weapons, which you'll have to do a lot, is very clunky and often gets you hit, but that might just be a skill issue.
One last thing I'd like to note is that this game is surprisingly extremely friendly to newcomers. There's two difficulties, "SUPEREASY" and "SUPERHARD", which sound like they're miles apart but in reality they're the same in gameplay, SUPEREASY just gives you infinite lives. It also allows you to change the speed of the game, which is absolutely not something I'd expect from a 1995 game but extremely welcome, though I didn't really use it.
There's a method to the madness, though. The game isn't amazing at communicating this to you (Alien Soldier is definitely the sort of game where you'd really need to read the manual, or just look up a guide today), but it's one of the most nuanced and rewarding action games of the era. Every system feeds into another one. At full health, your invincible dash turns into a powerful charge that consumes some health. Double tapping the attack button lets you do a short range attack that turns bullets into health, which means that if you play perfectly you can chain the above charge and shred through most bosses. All the weapons serve a purpose, both firing modes have their own uses (you can shoot while moving or standing still, but the former wastes a lot of ammo and isn't always viable, though sometimes necessary), and everything about the gameplay is very carefully considered. I don't know how Treasure did it, but even today Alien Soldier is such a tight and well-realized action game that few can match it.
... At its best, anyways. It is unfortunately marred by a couple of pretty annoying sections, around the mid-late game. There's a couple of stages (read: boss fights) where the environment is completely dark, and you need to fire to briefly light it up. This is hard on the eyes and generally very annoying, but not a big deal. There's a boss battle a bit later on, against a transforming mech, that has five phases, with no checkpoint. No other boss has more than one phase, which makes this by far the hardest fight in the game, even compared to the overall simple final boss. A difficulty spike isn't in itself a horrible thing, but two of the phases use a really annoying, clunky "flying" system where you're constantly wrestling against currents, which takes a lot to learn and shouldn't be something you have to figure out how to wrestle with well into a hard fight. It's way more frustrating than any other part of the game, which overall flows pretty well, and while it doesn't ruin it is is a sore spot. Also, switching weapons, which you'll have to do a lot, is very clunky and often gets you hit, but that might just be a skill issue.
One last thing I'd like to note is that this game is surprisingly extremely friendly to newcomers. There's two difficulties, "SUPEREASY" and "SUPERHARD", which sound like they're miles apart but in reality they're the same in gameplay, SUPEREASY just gives you infinite lives. It also allows you to change the speed of the game, which is absolutely not something I'd expect from a 1995 game but extremely welcome, though I didn't really use it.