Art and Visual Design
Late-era SNES at least, 2D N64/PSX/Saturn game at most. Think Sonic Mania. 3D models are acceptable but should be basic and limited (e.g. Yoshi’s Island).
Art style should be relatively faithful to the original SNES Panel de Pon, but with more detailed backgrounds. (Characters should stay adorable! The single-player artwork is the best reference for what they should look like, maybe a bit more proportionate.)
Settings should be whimsical and dreamlike but still relatively grounded in reality as in the first Panel de Pon, not cartoonish and farcical like the second. Mountains with sinister faces and volcano castles are OK, giant rubber ducks and piano footpaths are not.


Gameplay
A general side-scrolling platformer in the vein of those from the 4th-5th generation era.
Pseudo-metroidvania. Gameplay starts in a fairly large “hub” area with links to smaller “main” areas scattered throughout. In the middle part of the hub, where the player starts each session after continuing a save, is a fast-travel warp system to the various individual worlds. (Kirby and the Amazing Mirror, Shantae and the Pirate’s Curse, etc.)
If every character loses all health, the player is returned to the hub.

Gameplay follows a simple loop: hub -> sub world -> get new character -> boss -> hub until all four player characters are unlocked. After this, gameplay changes to hub -> main world -> receive upgrade from a certain character -> explore the new areas this opens up -> boss -> hub. Once this process is complete, the final area becomes available, possibly after a point of no return.

Each character has unique stats. HP determines how many health hearts the character starts with (can be extended with temporary hearts or permanent upgrades), strength determines how much damage is dealt to enemies and bosses with each hit, and speed is self-explanatory. This makes certain characters better for certain situations than others.

Character health is displayed in the top left corner of the screen. Taking damage will cause these hearts to complete (done in quarters).  Certain attacks will deal more damage than others, and some are OHKOs. When a fairy runs out of health, they are defeated and must be revived with a special item, although the player will automatically continue with the next girl in line. When all characters are out of health, it's game over. The player can then choose to either return to the hub or save and quit the game. (rewards for finishing the game with a low game over count?)

Displayed just below the health hearts is the magic bar. Lip will not be using this too much due to her melee focus, but it fuels most of the other girls’ moves and attacks. The magic bar is the same length for each character and can be upgraded with pickups (affecting all of them), but certain attacks and moves will drain it faster than others.

The player characters:
(Listed in order of unlock.)

Lip
HP: ***
Speed ***
Strength ***
Only default character.
Can walk on flower platforms that other characters can't use. Thiana’s upgrade lets her cause plants to grow that open up new areas.
As the main hero, she gets two upgrades. Ruby’s gives her the ability to create a jewel shield around her entire body, halving damage. It lasts for as long as you hold down the button. Release it to shatter the shield. This does less damage than her ordinary melee attack, but it has a wider range and can break through magical crystal walls.
Uses primarily melee instead of projectiles (her wand!). Thiana’s upgrade lets her use leaf projectiles at the expense of her magic bar.
With her wand, she's the only character who has an underwater attack by default.
The most balanced character. No outstanding flaws or any real strengths. A solid choice for (almost) any situation.

Windy
HP: **
Speed: *****
Strength: *
Powered up by: Sherbet and Seren
Can double-jump and glide with her wind magic. (Headcanon is flight, but that would make levels too easy.)
With Sherbet’s upgrade, she can temporarily freeze certain objects to use them as temporary platforms, the only way to access certain areas.
Attacks with mid-range wind puffs that push her back a bit.
Her movements carry the most momentum of any character, making her the most speedrun-friendly fairy.

Flare
HP: *****
Strength: *****
Speed: **
Built like a tank. HP and strength are high, but she moves slow and doesn't jump too high.
Relatively slow moving fire projectiles. A burning tackle melee attack (somewhat) makes up for low speed.
Immunity to fire, obviously. Fire-based hazards deal no damage. Lava deals steady health drain as opposed to instant death.
Seren’s power-up lets her turn into a shadowy form that is invisible to enemies and can bypass hazards the other playable characters can't. This causes the magic bar to drain VERY quickly though!
Worst swimming ability of any player character.

Elias
HP: **
Attack: *
Speed: ***
Frail, but versatile. Tricky to use, but rewarding to master. Good when precise underwater movements are needed.
As a water fairy, she has the best swimming ability of any playable character. Like the Frog Suit or Penguin Suit in the Mario series, she just has to press a direction to swim that way.
[undecided] Can sing a lullaby to temporarily put enemies to sleep. The music can activate certain switches and unlock special doors.
Projectile is a line of bubbles that are sprayed in a jet and can be angled up and down. Release to send them flying away individually, each traveling upwards in the direction Elias is facing.
Neris’s upgrade gives Elias an underwater attack consisting of a quick dash forward. Obviously this makes it possible to defeat enemies Windy and Flare would be helpless against, but it also lets her swim through strong currents to access new areas.

Pickups include:
Heart: Recovers half a health heart. Larger hearts heal more.
Magic Orb: Restores a bit of the magic meter. Larger orbs recover more magic.
GP: Spend back at the hub for consumables.

Consumables include:
Invincible: Temporary invincibility. Instant death hazards still kill.
Growth: Makes you bigger for a short time. You're slower and have a lower jump, but take less damage and hit harder.
Shrink: Opposite of the above. Faster and higher jump, but take more and deal less damage.