In Phantasmagoria of Flower View, Medicine Melancholy's spellcard background is spinning, while in Shoot the Bullet the flower pattern is static.

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In Phantasmagoria of Flower View, Medicine Melancholy's spellcard background is spinning, while in Shoot the Bullet the flower pattern is static.
Reisen Udongein Inaba and Tewi Inaba use the same spellcard background in Imperishable Night. Previously, I had the impression that the moon position was different, but it was because the moon was moving. So there is no difference between their backgrounds.
In Phantasmagoria of Flower View, Tewi had her spellcard background completely changed, which she also used in Shoot the Bullet.
Reisen Udongein Inaba's spellcard background. The background from Imperishable Night and Shoot the Bullet is the same, but the red eyes effect is not as emphasized in Shoot the Bullet (background is not turning red anymore).
In Phantasmagoria of Flower View, there is no red eyes effect and the overlayed spinning texture is not positioned on the moon, but rather somewhere at the top of the screen.
Eiki Shiki's spellcard background has been changed in Shoot the Bullet compared to Phantasmagoria of Flower View.
Evolution of Sakuya Izayoi’s spellcard background: Embodiment of Scarlet Devil ⟶ Imperishable Night ⟶ Phantasmagoria of Flower View ⟶ Shoot the Bullet ⟶ Impossible Spell Card ⟶ 100th Black Market.
In Imperishable Night, the main texture was changed from orange to red and an additional texture was added to the background. Since then, the images remained pretty much the same (with extremely small differences in brightness/contrast), but the final output looks quite different depending on game.
Marisa Kirisame's spellcard background is darker in Phantasmagoria of Flower View than in Imperishable Night. In Double Spoiler the hexagons became larger and the pattern doesn't seem to go up as fast as before. The background is brighter than in Phantasmagoria of Flower View.
If you look into the game files, the textures were slightly adjusted in Impossible Spell Card to be brighter than in Fairy Wars. But it's not really noticeable if you put the two in-game backgrounds side by side. There haven't been any other texture changes so far since Impossible Spell Card.
Overall, the general appearance of the spellcard background has remained the same since Double Spoiler (latest game where she appeared is Unfinished Dream of All Living Ghost at the moment of making this post 16-Jun-2023).
Reimu Hakurei's spellcard background is composed of two textures (a static one with a blue Yin-Yang orb and a rotating one with a red Yin-Yang orb).
In Double Spoiler, the red one has now both halves of the orb semitransparent, compared to only one half as it was in Imperishable Night and Phantasmagoria of Flower View.
Her background seems to have remained like in Double Spoiler in the following games until now (latest game where she appeared is Unfinished Dream of All Living Ghost at the moment of making this post 16-Jun-2023).
Evolution of Cirno’s spellcard background: Embodiment of Scarlet Devil ⟶ Perfect Cherry Blossom ⟶ Phantasmagoria of Flower View (same in Shoot the Bullet) ⟶ Double Dealing Character (same in Impossible Spell Card) ⟶ 100th Black Market.
The texture has been the same since Phantasmagoria of Flower View, but it seems like different effects have been applied to it in the following games so it appears darker/lighter.