If this is an April Fool's joke, I'd be impressed. This is an extremely well-polished early access demo for a game that looks to have much potential, and furthermore would take a lot of effort to make.
Also Nupuryu has already mentioned in Ci-En about plans to make a Slay the Spire-style game after Ruins Seeker in the past.
By the way, as with the previously-locked thread for this game, this project is also a collab work with Atelier Choice (the creator of Lelie's Navigation, among others). From the trial, I'd assume that the scenes and fetishes included would have common themes to both creators.
Controls:
While this game is entirely playable (and intended to be played with) only the mouse, you can still use arrow keys/WASD to move, enter/Z to talk/confirm, X to open the main menu, etc.
With the mouse, left-click does the same thing as Z does - talk to characters, examine objects, start events, etc.
Right-click opens the main menu, hides the current dialogue box, etc.
Mousewheel opens the backlog.
In combat, hover over the enemy to view its stats, and hover over status effects to view what they do. Hover over cards to see what they do (the descriptions are in Japanese, of course). Left-click cards to use them. You can use cards as much as you have CP/MP (the number over the "END" button), with each card costing a different amount. As of the early access trial, you automatically get a fixed 4 CP each turn (no carry-over). The "END" button ends the player turn. Cards are taken from the current active deck depending on a card draw stat. In the early access trial, this is 4. Both used cards and unused cards in hand are discarded, and will not return until you exhaust the entire deck and get a brand new one. However, there are also cards that when used are "banished" and will not return until the end of the battle.
It's not freely used as of now because everything is an event battle, but using the card "Access" transforms the main character, discards all cards in hand, refreshes CP, and allows you to fight better for a limited amount of time (unlimited in the early access trial's event battles).
Story tidbits:
The setting is some kind of SF megatopia so advanced that even clothes can be made out of data. Most people, with the ability to use "Devices", live with high standards. However, those who can't use "Devices" are named "Storage" and live a third-class citizen life. However, threats named "Trash" roam free outside, and it's up to the local governmental peacekeeping force to eliminate "Trash" for the greater good.
Our main character, Romasha Patience (unwanted nickname: "Princess Romance") is one such member of the peacekeeping force, specifically the all-female 4th Division, and among the entire base is basically the "golden child" with top-level looks, top-level popularity, friends in high places, a genuinely nice personality, and absolutely zero practical combat experience (basically everyone refuses to have her out on assignments). Maybe it's also thanks to that, but she's been singled out by a thug of the 0th Division, the "black sheep" group consisting entirely of former "Storage".
Our story begins with what would have been an ordinary day, were it not for the wheels of destiny causing a series of events that in the end result in Romasha under probationary surveillance, her Device completely reset, and for the first time ever given tasks outside.