So to me, the Valis games are the PC Engine releases, though the SNES Valis IV gets honorable mention.
I say this because the PC Engine is where the game really came to prominence and became popular - it’s the only platform with all four main-series games on it after all. So what are the qualities of a Valis game?
short-range projectiles. Every Valis game gives Yuuko a sword, but the sword shoots projectiles. The projectiles don’t usually go the full length of the screen, making your strikes more tactical and less flailing.
attack resource management. This can be in the form of attacks, ala Valis III, where your sword takes a while to recharge (this can be powered up). Basically you’ve got a gauge that fills. At the top it’s strongest, and your projectile will go the furthest. But it immediately depletes when you hit the attack button, so if you attack again right away, your attack will be weak. With other characters, your projectile will take a long time to return, or be really short, or etc.
magic management. Valis characters can usually carry one magic type at a time. Sometimes they can give it more charges with powerups, sometimes it’s single use in a rotation, but one way or another, magic is something you have to collect and manage. Different characters do different magic attacks.
female protagonist. This is a given, but a lady with a skirt or dress is pretty much necessary.
the slide. I’ve written about this elsewhere, but the slide was a central mechanic to valis before things like double jumps really took off (valis got that later). There were pits you could only clear by sliding, and obstacles you could only clear with a slide. Platforming was build somewhat around the slide, which I think is important. The slide also does damage at a certain point, which is interesting.
vertical level design. the slide is your best tool, so vertical level design makes you work to use it. Not every Valis level has a vertical component, but many do. There’s a lot of ascending in this series.
big shoulderpads, big story. The story is always epic and the shoulderpads/guards just get bigger with every game. When she gets the super armor she’s got four shoulder guards. why not!!
character switching. This is only really in later valis games, and I don’t think it’s necessary to be a valis game (1 and 2 don’t have it), but much was made of it back in the day so it’s worth mentioning.
then there’s a bunch of vague vibe stuff, like running on rooftops, cool music, modulated VO for enemies, etc.
I wrote about this on gamasutra but I particularly like looking at Valis IV vs Super Valis IV. Here’s what I wrote at the time.
Super Valis IV is the final action game in the (not very) popular Valis series. The series as a whole generally stars girls with swords, running on rooftops and through castles and cities, swinging weapons and jumping through platforms to defeat a host of evildoers from beyond. Super Valis IV is the Super Nintendo port of the original Valis IV for PC Engine. And a lot of people hate it.
I had foolishly believed what the few reviews on the internet said - this game was too short, and it was a pale imitation of the original. So I waited until this year to play this game for the first time, and I found they were very wrong, at least about it being bad. Sure, it loses most of the cutscenes, and a couple levels are dropped, but it’s incredibly interesting to me as a remix of an existing game, like a chopped and screwed version of a popular tune.
Where Valis IV had three characters you could switch between on the fly, Super Valis IV streamlines to one. Super ditches the slide move for a dash, and the double jump (which you had to switch characters to access) for a dashing jump. To accommodate this, all the levels were completely redesigned to be more horizontal than vertical, and to place secrets behind horizontal leaps of faith, rather than vertical drops.
The port also completely revamps the magic and attack systems. Where the original used a cooldown-based magic system and an attack that could be powered up to reach far across the screen, the port shortens the attack, while magic now comes from a host of limited-use collectible items. You can store five magic types at a time, and can select between them to use magic whenever you like, so long as you keep an eye on your inventory.
On top of this, the music has been completely redone, and right from the title screen takes a darker tone, even though the original is technically the darker game, with crucified women and severed limbs all over the place. And it plays extremely well. Everything they try to do works. So what if it has fewer levels that have all been remixed? It is a very interesting lesson in game design - how do you take a completed game and make a new version that actually plays differently, using many of the same assets? Modders would figure this out later, but this is an excellent early example.
Something I missed in this writeup is that - to continue the speed-oriented nature of this “remix,” you can always see the boss’s health meter on the bottom of the screen. It fills up more the longer you take! So if you speedrun your way there, the boss will take fewer hits to kill. That’s pretty neat!
Well, hopefully that gets at some of it.
I think short projectiles and consumable magic are two of the big ones, but Valis tried a lot of things at once, so it’s kind of a grab bag. It sits somewhere between a castlevania and a mega man x and a contra, but set in a totally different world than any of those. It’s cool I think! I would like to own that franchise some day.