This is a resource pack that's mainly for immediate visual effects, although there's a bit more to it than that, the main purpose to it is to make the main hotbar area more appealing, at least for me personally.
A full list of everything in this resource pack is as follows:
Please keep in mind that some textures didn't exist back then, for example there was no "flashing absorption heart" in the old files, so that's a perk of using modern Minecraft.
And the final thing is
The graphics are as follows (For Hardcore first, then Survival):
Please note that "default" in this context does not mean "untextured," it should mean "these are the hearts you start with no matter what, they're a fallback heart when you don't have any effects." I just used "default" for short. Thank you.

The wither effect

The poison effect

The freezing effect

The absorption effect, along with the default red heardcore hearts
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Here we are, heading on to the next phase: Normal (retextured).

The wither effect

The poison effect

The freezing effect

The absorption effect on survival hearts, as well as the default red survival hearts
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And here's the final phase: Animals.

Animal hearts and fully charged jump bar

Animal hearts and cooldown bar

Animal hearts and jump bar background
And that's it! I hope you enjoy.
If you want to find more, my PMC is https://www.planetminecraft.com/member/garnishhat/