Positron is my attempt at introducing actually meaningful changes to the game. From food to mining ores to the world, the pack's philosophy attempts to overhaul specific areas of the game in ways that introduce an intentional design direction to the game.

This pack is not feature complete yet.

Current notable features:

Food & Farming Overhaul

Exhaustion builds substantially slower, allowing you to eat less food
Hunger/saturation is no longer linked to health regeneration, excluding damage from starvation
Players naturally regenerate slowly
Food is generally harder to obtain: crops grow slower, animals have longer breeding cooldowns and drop less food, baby animals take longer to grow
Maintaining diversity in diet gives helpful buffs

Vanilla Minecraft has a number of foods, but for the most part eating is simply a chore and the game forces you to stuff your face in the middle of combat, or if you even so much as blink. These tweaks encourage players to seek out a variety of foods and eat at a relaxed pace, and don't take away from the survival aspect. Additionally, health-regenerating items like potions become far more useful in combat now that hunger and saturation do not help with healing.

Mining Changes

All regular "blob" (vanilla) ore generation generates slightly less
Huge scattered deposits of ores can be found occasionally underground

Mining in vanilla is largely the sameish everywhere and only changes the deeper you go. Huge ore deposits provide much needed variety and satisfaction to the mining process, also encouraging the construction of transportation infrastructure to these regions for repeated mining trips.

Transportation Changes

Horses are substantially easier to use (Horseman, Vanilla Backport)
Furnace minecarts can load chunks and run faster, using copper rails allows for greater speeds, powered rail recipe makes more (Modern Minecarts)
Elytra cannot be boosted with fireworks anymore, instead flying over campfires provides lift (Aileron)

Minecarts in vanilla are largely too slow and expensive to employ most of the time in vanilla, being usually outclassed by other methods. Elytra essentially invalidate any method of transportation once you acquire one. Horses are just a pain. Ultimately, building is a core aspect of Minecraft, and thus Positron should emphasize it wherever possible. So, minecarts have been buffed and elytra have been tweaked to require building infrastructure. Horses are tweaked to become a more viable method of exploration, as well as more accessible early-game by giving saddles a recipe.

Enchanting/Exploration Changes (Incomplete)

The enchanting table now uses an enchanting tree, requiring specific Ancient Books found in chests to unlock enchants as well as catalyst items (Immersive Enchanting)
New structures with structure-unique pools of enchanted tools/armor can be found in the world
New ender eyes may be found in these new structures (End Remastered)
The spyglass and camera (Exposure) are now uncraftable items unique to two new structures
Enchantments may be ripped from enchanted equipment to a book

Vanilla biomes often have little excuse to visit them aside from their looks. With these tweaks and introducing structures unique to certain biomes with genuinely useful loot (enchanted items, uncraftable artifacts), players may now actually want to, for example, seek out the Forge in snowy taigas or groves for its Protection-enchanted equipment and transfer the enchantment to their own armor, or look for a cherry grove's Photography House to acquire its camera and film. Instead of frustrating, boring rerolls on a vanilla enchantment table, players have to set out intentionally for their enchantments. Additionally, the ender eyes introduced by End Remastered may be found in a few of these new structures

Note: Many biomes do not yet have a unique structure as planned, and enchantment trees have not been completed for all enchantments.

Miscellaneous Changes

Bigger stack sizes (up to 512)
Experience rewards from more sources (advancements, opening loot chests, farming)
Thicker fog, grows with depth beneath sea level, environmental particle effects, and more visual tweaks
Audio tweaks such as reverb, more satisfying footsteps and more frequent music
A number of backported features from newer versions
Killing fish with a trident guarantees the fish drop :)