The original Mugen Senshi Valis was created by the famed Wolf Team, and just like their other early game, Final Zone, it's one of the worst games ever made. Basically, it's a side-scrolling action game like Ghosts'n Goblins or Castlevania, but much like many of the infamous Euro platformers later, it features vast multiscrolling mazes in place of the short, tightly designed stages of its Japanese contemporaries. There's always an arrow on screen to point the player in the right direction, but following it too closely means missing out on most of the powerups. But even just the direct path to the boss is ridiculously long, and there's nothing interesting in between. The same portions are literally copied and pasted next to each other dozens of times, so without the helpful arrow Yuko would be hopelessly lost.
Still the game wouldn't be quite as insufferable if the controls weren't as inept as they are. Yuko has a weird double-tiered jump, where she gets another boost in mid-air when the button is held down (and this being a computer game, the button for jump of course is "up"), yet they're Castlevania style "stiff" jumps, where the direction and trajectory is strictly fixed. The problem is, her extended jump is so long it's almost impossible to guess beforehand where she'll land exactly. And that's before she gets hit by an enemy in mid-air and is pushed back in the opposite direction. So far that's period-appropriate, but on top of that there is no recovery time after a hit, so usually Yuko gets flailed around helplessly multiple times, before she can land on her feet again, more often than not even further back then where she started out. And since the stages are mostly copy & paste, when Yuko falls down a screen in a climbing segment, she usually keeps falling for quite a long stretch.
Most players' first impulse would be to clear a screen of enemies before attempting any risky jumps, but that's no use here: The monsters keep respawning endlessly, no matter whether Yuko is running around or standing still. They attack relentlessly, and there's not a second to relax. Most attackers come from above, and thanks to the choppy gameplay, fighting off flying enemies reliably is simply not possible.
Every once in a while, Yuko happens upon powerups that improve her armor or upgrade her sword with different types of projectiles, which is an absolute necessity, as trying to hit enemies with the basic sword strike only ever ends in tears. But nothing comes for free in Vecanti - each upgrade consumes several bars of health when picked up. The more powerful the weapon, the more it damages Yuko first. If she actually doesn't have as much health as the item costs, she is scolded with the message "Ill gotten goods never prosper!", and suddenly the flying enemies start an insane bombardment of bullets that kill her within seconds. Yuko's only saving grace is her ability to charge up her health bar a hundred times by picking up capsules left behind by defeated enemies. That's right Wolf Team managed to introduce grinding to an action game. Really the only way to get through most of the bosses is to find a spot where mostly ground-based enemies attack and to grind up a few dozen health bars before jumping into the boss' screen-filling streams of bullets and try to defeat them in a war of attrition. Most vital is a healthy pocket of charged bars before entering stage 3, because that only has flying enemies, which invariably means that Yuko will end it with much less health than she started with.
This is how the cutscenes would have looked like on a blurry old screen.
Mugen Senshi Valis might be a horrible, unplayable mess, but its call to fame to begin with wasn't the gameplay, but the pioneering in cinematic cutscenes - two years even before Ninja Gaiden. That achievement has to be put in perspective, though, as the cutscenes consist almost entirely of close-ups of anime heads, with very few exceptions. There are a few instances of scrolling along a character's full body view, but the sole bit of action is the scene where Reiko draws her sword and points it toward her friend/rival, before they have their duel to the death. What's left is the quite excellent chiptune music, really the only part the original Valis is worth being remembered for. Fortunately the PC-88 and FM-7 versions contain a music jukebox (accessed by pressing F5 on the title screen), so no one actually has to play the game to enjoy the it.
Mugen Senshi Valis first came out for NEC's PC-88, but was soon ported to other Japanese home computers. There was a release for the PC-98, but it's just the same as the PC-88. The Sharp X1 version also uses the exact same graphic tiles and plays the same as the original, but the music consists only of Game Boy quality bleeps and bloops.
There's also a hidden bonus round that contains all weapons and heals Yuko at the end.
The FM-7 port on the other hand was tweaked quite a bit. Yuko can now change directions during a jump, and the platforming is not quite as relentless as a result. Enemies still have her bounce back and forth in a continued, hopeless pummelling, but their spawning behaviour is much less insane, too. Powerups now simply cannot be grabbed when Yuko's life bar doesn't afford it, instead of just killing her off for trying. In this form the stages are actually manageable, but they're still endless boring areas you have to get through with annoying physics. The bosses on the other hand have gotten even harder, as they can only be hurt by hitting their heads. Yuko can also get caught in between their countless bullets and get pretty much all her life sucked out of her. When encountering a stage boss, the background is dimmed, but Yuko can keep running around the entire stage, while the boss keeps respawning near her.
Other than the previous two computers, the FM-7 version is displayed in low resolution mode, with all the graphics redone without dithering. Back then on old blurry screens, the high resolution versions probably looked better, but on a modern crispy sharp monitor, they look a bit unclean, so now the FM-7 version is actually a bit better for it. The cutscenes are still in dithered high resolution, though. Music on the FM-7 is about on par with the PC-88 original, although it sounds a little bit softer.
There was also a version for the MSX(1) standard, which of course looks and sounds terrible. The MSX' lower capabilities actually help out the player, as there are never more than two enemies on screen at a time, but the controls are worse than ever. Yuko's long jump now works somewhat like a double jump. At least it cannot be done anymore by just holding "up" pressed, but instead it has to be pressed twice with the appropriate timing. But other than the FM-7 version, it's still not possible to change directions in between. Bosses are all fought in front of an empty night sky, so Yuko can't even use the terrain in her favor. All the cutscenes are gone, and so are half of the stages, which in the case of Mugen Senshi Valis is a good thing: Less game only means less suffering.